Examples are partial payloads: omitted context is not shown. All code examples are valid JSON.

Every normal webhook event request contains the following two objects in the payload:

• event Contains metadata about the event.
• sender Contains the details of the workplace that is sending the event.

Most webhooks, with the exception of a few like backgroundPoll, also contain the following object:

• session Contains the details of the current session.

Then there are some objects that only occur with specific webhook events:

• scanCode (scanned-code events and requested-scan follow-ups)
  Contains the scanned code’s details.
• addSessionLine (only occurs with addSessionLine event)
  Contains the added line’s details.
• updateSessionLine (only occurs with updateSessionLine event)
  Contains the updated line’s details.
• removeSessionLine (only
  occurs with removeSessionLine event)
  Contains the removed line’s details.
• mergeSession (only occurs with mergeSession event)
  Contains the ID of the session that the current session is merging with.
• moveSession (only occurs with moveSession event)
  Contains the table number that the session is being moved from and to.
• completeSession (only occurs with completeSession event)
  Contains the payment details of the session.
• creditSession Contains payments associated with crediting a session.
• determinePricing Contains pricing context.
• selectRelation (only occurs with selectRelation event)
  Contains the selected relation details.
• printBill (only occurs with printBill event)
  Contains the details of previous payments to the bill.
• customAction (only occurs with customAction event)
  Contains the details of the custom action.
• course (only occurs with kitchen…Course event)
  Contains the details of the underlying course.
• externalPayment (only occurs with …ExternalPayment event)
  Contains the external payment’s details.
• cafeteriaOrder
  Contains the details of the underlying cafeteria order.
• tableOrder
  Contains the details of the underlying table order.
• order
  Contains the details of the underlying order.
• table
  Contains the details of the underlying table.

Finally, some objects may only occur in certain circumstances.

• dialog (only occurs after a dialog response)
  Contains selected dialog options.
• form (only occurs after a form response)
  Contains submitted form values.
• openUrl (only occurs when the client supports it)
  Contains preferences regarding usage of the openUrl response.

An invalid reply can cause an error notification. This uses an error and original envelope, with the original event and sender nested under original; it does not have the normal top-level envelope. Some transport, timeout and authentication failures are not sent back to the endpoint:

• error
  Signify an error in the response that was sent.

When replying to a webhook, return a JSON object containing the applicable response properties below. An empty body is accepted for most events, but not for startExternalPayment. Some properties are scalars or arrays rather than objects.

• error
  Signify an error in the request that was sent.
• scanCode (only works with scanCode)
  Response to the scanCode event.
• lineChanges
  Request changes to the session’s lines.
• lineAdditions
  Request additions to the session’s lines.
• lineDeletions
  Request deletions from the session’s lines.
• lockSession
  Lock the session from further changes.
• lockSessionForAdditions
  Lock the session from further additions (deletions/decreases is allowed).
• receiptFooter (only works with completeSession)
  Request some extra data to be printed on the footer of the receipt.
• billFooter (only works with printBill)
  Request some extra data to be printed on the footer of the bill.
• dialog
  Request a dialog to show up on screen.
• form
  Request a form with various input fields to show up on screen.
• message
  Request messages to show up on the user screen and/or the customer screen.
• requestScanCode
  Request a code to be scanned in the POS.
• displayBarcode
  Display a code on the POS customer display.
• hideBarcode
  Instantly hide a code that is currently displayed.
• openUrl
  Display or redirect to a website
• customActionChange
  Change the caption of a customAction button.
• vatMethodChange
  Change the VAT method of the current session.
• externalCardScan
  Notify the POS that an external card was scanned, that the POS should know about.
• prepayTable
  Register payment on a table.
• requestCustomAction
  Request the POS to execute a specific custom action.
• entityAnnotations Replaces this consumer’s annotations for an entity.
• version
  A string that represent the version of your external software (or webhook middleware).
• externalPayment (only works with …ExternalPayment)
  Influence the currently running external payment.

For a polling event (event.eventPolling: true), explicitly return polling.finished to control whether polling continues. External-payment completion and certain background-poll responses also end the current request; see polling.

• polling Tell MplusKASSA to continue polling or not, and optionally display some messages.

---

Event reference and response rules

All normal events use event and sender, with session when supplied by the caller. Follow-up dialog, form, scanCode and openUrl context can accompany the applicable event. Event availability depends on configuration and the sending application.

Event	Purpose	Additional request payload
startSession	Start a session.	No additional event-specific object.
scanCode	Process a scanned code.	scanCode
addSessionLine	Add a session line.	addSessionLine.line
updateSessionLine	Update a session line.	updateSessionLine.line
removeSessionLine	Remove a session line.	removeSessionLine.line
pauseSession	Pause a session.	No additional event-specific object.
resumeSession	Resume a session.	No additional event-specific object.
startPayment	Enter payment processing.	No additional event-specific object.
cancelPayment	Cancel payment processing.	No additional event-specific object.
mergeSession	Merge sessions.	mergeSession
moveSession	Move a session between tables.	moveSession
cancelSession	Cancel a session.	No additional event-specific object.
completeSession	Complete a session.	completeSession.payments
creditSession	Credit a session.	creditSession.payments
startExternalPayment	Start an external payment.	externalPayment
pollExternalPayment	Check external-payment status.	externalPayment
requestCancelExternalPayment	Request external-payment cancellation.	externalPayment
cancelExternalPayment	Notify external-payment cancellation.	externalPayment
customAction	Invoke a configured custom action.	customAction
backgroundPoll	Background polling.	No additional event-specific object.
printBill	Print an intermediate bill.	printBill.prepayments
kitchenStartCourse	Start a kitchen course.	course; optional order, tableOrder, cafeteriaOrder, table, relation.
kitchenCompleteCourse	Complete preparation of a kitchen course.	course; optional order, tableOrder, cafeteriaOrder, table, relation.
kitchenServeCourse	Serve a kitchen course.	course; optional order, tableOrder, cafeteriaOrder, table, relation.
startPOS	Start the POS application.	No additional event-specific object.
openPOS	Open the POS.	No additional event-specific object.
closePOS	Close the POS.	No additional event-specific object.
exitPOS	Exit the POS application.	No additional event-specific object.
selectRelation	Select or deselect a relation.	selectRelation.relation
determinePricing	Request pricing evaluation.	determinePricing

Successful endpoint replies should use HTTP 200. The implementation parses JSON bodies for HTTP 200 and 400; an error object marks the response as an error even when delivered with HTTP 200. A nonempty reply must be a JSON object. Unknown properties can be ignored, so acceptance alone does not demonstrate support. Interactive response processing requires a blocking event.

Session edits require a supplied session and are rejected for completeSession, creditSession, cancelSession and pauseSession. This restriction covers line additions/changes/deletions, session locks and VAT-method changes. Line edits are additionally rejected when the session contains an invoice or receipt reference. Ownership, article lookup and consumer settings impose further checks.

scanCode responses are specifically parsed for scanCode events; receipt footers for completeSession; bill footers for printBill; and externalPayment responses for the four external-payment events. The shared response properties are still subject to their own validation and client capabilities. Sending a response property does not create a guarantee that it can be executed in every event.

Request objects

event

{
    "event": {
        "eventBlocking": true,
        "eventCounter": 1,
        "eventTimestamp": "2017-08-09T16:07:33.964+02:00",
        "eventPolling": false
    }
}

Property	Type	Explanation
event.eventBlocking	boolean	Is the event blocking? When this is true, MplusKASSA is waiting for your response.
event.eventPolling	boolean	Is the event polling? When this is true, MplusKASSA will continue to query your endpoint until you respond that polling is finished (see polling response).
event.eventCounter	int	An increasing counter that helps you check if you already processed an event. Please note that the counter may occasionally reset.
event.eventTimestamp	datetime	The date and time that the event occurred.

The event name is not a property of event; it is conveyed separately from this JSON object. eventCounter is a 64-bit integer and is not globally unique; retain sender context when identifying deliveries. Timestamps are ISO 8601 strings with a timezone offset. Optional fields may be omitted; arrays built from available entries may also be absent when empty.

sender

{
    "sender": {
        "branchNumber": 1,
        "browser": {
            "browserFamily": "Chrome Mobile",
            "browserVersion": "109.0.5414",
            "deviceType": "Mobile",
            "platformFamily": "Android",
            "platformVersion": "10"
        },
        "hasReceiptPrinter": true,
        "employeeNumber": 6,
        "instanceId": "f9fac333-9fa7-45fe-8e9c-2c1e6465942f",
        "language": "nl",
        "paymentStarted": false,
        "productName": "MplusQservice",
        "versionNumber": "48.0.0",
        "workplaceNumber": 1
    }
}

Property	Type	Explanation
branchNumber	int	The branch the event was sent from.
workplaceNumber	int	The workplace the event was sent from.
instanceId	uuid	Every time the POS is restarted, this UUID is regenerated.
paymentStarted	boolean	When the POS is in the payment screen, this variable will be true. To detect changes to and from the payment screen, you can listen to the startPayment and cancelPayment events.
productName	string	Whether the webhooks are triggered from the Desktop POS MplusQ or through the API MplusQservice.
Browser details have been added in v48.0.0
When webhooks are triggered through one of our web apps, this will contain information about the browser that was used.
browserFamily	string (optional)	The browser used.
browserVersion	string (optional)	The version of the browser used.
deviceType	string	Mobile, Tablet, Desktop, or Bot
platformFamily	string (optional)	The platform (or OS) used.
platformVersion	string (optional)	The version of the platform used.
hasReceiptPrinter was added in v57.0.0
hasReceiptPrinter	boolean (optional)	Whether the workplace has a receipt printer configured.

Property	Type	Explanation
sender.employeeNumber	integer	Currently logged-in employee number.
sender.versionNumber	string	Version of the sending application. Available by MplusKASSA v17.0.0.
sender.language	string	Normalized language: eng becomes en, deu becomes de, an empty language becomes nl; other values are lowercased. Available by MplusKASSA v47.0.2.
sender.activity	object (optional)	Current activity, when available; see below. Available by MplusKASSA v14.0.0.

Browser properties above are nested under sender.browser and are emitted only when nonempty. sender.hasReceiptPrinter is separate from browser. Printer status fields such as overallState, coverState, paperState and ageInSeconds are not emitted by this serializer.

Activity

The same activity structure is used by sender.activity and determinePricing.activity.

Property	Type	Explanation
activityId	uuid	Activity identifier.
activityNumber	string	Activity number/reference. Available by MplusKASSA v47.1.0.
description	string	Activity description. Available by MplusKASSA v47.1.0.
interfaceLayoutId	integer or null	Interface layout ID; null when not positive. Available by MplusKASSA v47.1.0.
articleLayoutId	integer or null	Article layout ID; null when not positive. Available by MplusKASSA v47.1.0.
location	string	Activity location. Available by MplusKASSA v47.1.0.
priceGroupNumber	integer or null	Price group number; null when not positive. Available by MplusKASSA v47.1.0.
employeeStartTimestamp	datetime or null	Employee start timestamp. Available by MplusKASSA v47.1.0.
employeeEndTimestamp	datetime or null	Employee end timestamp. Available by MplusKASSA v47.1.0.
managerStartTimestamp	datetime or null	Manager start timestamp. Available by MplusKASSA v47.1.0.
managerEndTimestamp	datetime or null	Manager end timestamp. Available by MplusKASSA v47.1.0.
activityTypeId	integer or null	Activity type ID; null when not positive. Available by MplusKASSA v47.1.0.

session

{
    "session": {
        "sessionId": "5eea25d4-4188-43b8-9a66-8086561d590c",
        "table": {
            "number": 11,
            "subNumber": 4
        },
        "relation": {
            "relationNumber": 54,
            "extRelationId": "CST042",
            "name": "John Doe",
            "address": "",
            "zipcode": "",
            "city": "",
            "country": "",
            "deliveryAddress": "",
            "deliveryZipcode": "",
            "deliveryCity": "",
            "deliveryCountry": "",
            "telephone": "",
            "mobile": "",
            "email": "",
            "cardNumber": "",
            "bankAccountNumber": "",
            "vatNumber": "",
            "commerceNumber": ""
        },
        "lines": [
            {
                "lineId": "c686f63d-46a7-498e-b421-c72e5cb7136b",
                "extLineId": "External line reference #32424",
                "articleNumber": 1,
                "priceIncl": 2.5,
                "quantity": 1,
                "text": "Coffee",
                "discountPercentage": 50,
                "discountAmount": 1,
                "barcode": "8712345678901",
                "supplierArticleNumber": "XR-123",
                "pluNumber": "9864",
                "extArticleId": "651",
                "externalDiscount": {
                    "discountId": "d2091980-7e7d-11e7-bb31-be2e44b06b34",
                    "discountDescription": "Sample Voucher",
                    "discountPercentage": 10,
                    "discountAmount": 2
                }
            }
        ],
        "invoice": {
            "invoiceId": "3ce511eb-1ef2-4d36-8057-8a2d7f51aebe",
            "year": 2025,
            "number": 113
        },
        "payments": [
            {
                "amount": 1,
                "description": "With cash",
                "method": "CONTANT"
            }
        ]
    }
}

Property	Type	Explanation
session.sessionId	uuid	The session’s unique ID.
session.table.number	bigint (optional)	The table number that the session is attached to.
session.table.subNumber	bigint (optional)	The table sub number that the session is placed upon.
session.lines	array	The session’s lines.
session.lines[].lineId	uuid (optional)	The line’s unique ID.
session.lines[].articleNumber	bigint (optional)	The line’s article number.
session.lines[].priceIncl	number (optional)	The line’s price including VAT.
session.lines[].quantity	number (optional)	The line’s quantity.
session.lines[].text	string	The line’s textual description.
session.lines[].discountPercentage	number (optional)	The line’s percentual discount, this stacks with the discount amount.
session.lines[].discountAmount	number (optional)	The line’s discount amount, this stacks with the discount percentage.
session.lines[].supplierArticleNumber	string (optional)	Article number from the supplier, if available.
session.lines[].pluNumber	string (optional)	PLU number, if available.
session.lines[].extArticleId	string (optional)	External article ID, if available.
Note that you would normally not be able to have a line with a discount from MplusKASSA and an external discount. It can only be one or the other.
session.lines[].externalDiscount.discountId	uuid (optional)	This is a UUID you generate and store to remember that you applied this discount.
session.lines[].externalDiscount.discountDescription	string (optional)	A textual description for the external discount.
session.lines[].externalDiscount.discountPercentage	number (optional)	The line’s external percentual discount, this stacks with the external discount amount.
session.lines[].externalDiscount.discountAmount	number (optional)	The line’s external discount amount, this stacks with the external discount percentage.
Note that you would normally not be able to have a line with a discount from MplusKASSA and an external discount. It can only be one or the other.
session.payments[]	payment (optional)	The session’s payments, including any prepayments that were made at any point in its history. Available by MplusKASSA v55.0.8.
Look at the completeSession object for a description of the payment’s properties.

Additional session properties

Property	Type	Explanation
session.totalInclAmount	number (optional)	Total including VAT.
session.totalExclAmount	number (optional)	Total excluding VAT. Available by MplusKASSA v18.0.0.
session.paidAmount	number (optional)	Paid amount on the underlying sale. Available by MplusKASSA v21.3.0.
session.prepaidAmount	number (optional)	Prepayments on the underlying order. Available by MplusKASSA v21.3.0.
session.openAmount	number (optional)	Outstanding amount: total including VAT minus paid and prepaid amounts. Available by MplusKASSA v21.3.0.
session.order	object (optional)	Underlying order; see order. When a sale combines multiple orders, the current conversion includes only the first order reference.
session.invoice	object (optional)	Invoice reference: invoiceId (UUID), year (integer), number (64-bit integer). Available by MplusKASSA v10.0.3.
session.receipt	object (optional)	Receipt reference containing receiptId (UUID). Available by MplusKASSA v16.1.0.
session.cafeteriaOrder	object (optional)	Underlying cafeteria order; see cafeteriaOrder.
session.webhookConsumerId	uuid (optional)	Webhook consumer associated with the session, when supplied. Available by MplusKASSA v61.0.0.
session.salesBaseId	uuid (optional)	Underlying sales record ID. Available by MplusKASSA v61.0.0.
session.salesTypeId	string (optional)	Underlying record type: order or turnover in the current converter. Available by MplusKASSA v61.0.0.
session.nutritionalData	object (optional)	Aggregated nutritional values when ingredient functionality is licensed and nutritional data exists. Available by MplusKASSA v16.1.0.

Additional session-line properties

The same line structure is used recursively and in addSessionLine.line, updateSessionLine.line and removeSessionLine.line. Article-specific pricing, VAT, identifiers, discounts and amounts are emitted only when articleNumber is present. lineId itself can be omitted when unavailable.

Property	Type	Explanation
session.lines[].extLineId	string (optional)	External line reference, omitted if empty. Available by MplusKASSA v16.1.0.
session.lines[].barcode	string (optional)	Article barcode. Available by MplusKASSA v14.0.0.
session.lines[].priceExcl	number (optional)	Unit price excluding VAT. Available by MplusKASSA v18.0.0.
session.lines[].vatCode	integer (optional)	VAT code. Available by MplusKASSA v11.3.0.
session.lines[].vatPercentage	number (optional)	VAT percentage. Available by MplusKASSA v11.3.0.
session.lines[].totalInclAmount	number (optional)	Line total including VAT.
session.lines[].totalExclAmount	number (optional)	Line total excluding VAT. Available by MplusKASSA v18.0.0.
session.lines[].turnoverGroup	integer (optional)	Turnover group number. Available by MplusKASSA v14.0.0.
session.lines[].allowPointsDistribution	boolean (optional)	Whether points may be awarded for this line. Available by MplusKASSA v14.0.0.
session.lines[].allowPointsPayment	boolean (optional)	Whether points may be used to pay for this line. Available by MplusKASSA v14.0.0.
session.lines[].allowDiscount	boolean (optional)	Whether this line allows discount. Available by MplusKASSA v14.0.0.
session.lines[].preparationMethods	array of lines (optional)	Preparation-method sublines, using this same line structure. Available by MplusKASSA v14.0.0.
session.lines[].componentArticles	array of lines (optional)	Component-article sublines, using this same line structure. Available by MplusKASSA v14.0.0.

Money is serialized to two decimal places, discount percentages to four and quantities to ten. Internal line consumer IDs and external-discount discountType are not emitted by the request-line serializer.

Relation

cardNumbers: available by MplusKASSA v60.6.0.

A relation has relationNumber (64-bit integer) and name (string). The following strings are optional and omitted when empty: extRelationId, address, zipcode, city, country, deliveryAddress, deliveryZipcode, deliveryCity, deliveryCountry, telephone, mobile, email, cardNumber, bankAccountNumber, vatNumber, and commerceNumber. cardNumbers is an optional array of strings containing all card numbers; the standard converter also sets cardNumber to the first entry. This structure is shared by session.relation, selectRelation.relation, determinePricing.relation and the optional top-level relation on kitchen events.

Nutritional data

Each field below is an optional number under session.nutritionalData. Values follow the configured nutritional data; this serializer does not attach units or convert units.

Property	Type	Explanation
calories	number (optional)	Energy in the calorie-based nutritional field.
joules	number (optional)	Energy in the joule-based nutritional field.
fat	number (optional)	Fat.
saturatedFat	number (optional)	Saturated fat.
monounsaturatedFat	number (optional)	Monounsaturated fat.
polyunsaturatedFat	number (optional)	Polyunsaturated fat.
carbohydrate	number (optional)	Carbohydrates.
fiber	number (optional)	Fiber.
starch	number (optional)	Starch.
sugar	number (optional)	Sugars.
protein	number (optional)	Protein.
sodium	number (optional)	Sodium.
calcium	number (optional)	Calcium.
iron	number (optional)	Iron.

scanCode

{
    "scanCode": {
        "scannedCode": "8712345678901",
        "codeType": "barcode"
    }
}

Property	Type	Explanation
scanCode.scannedCode	string (optional)	A textual representation of the code that was scanned.
scanCode.codeType	string (optional)	barcode, rfid

Property	Type	Explanation
scanCode.requestId	integer (optional)	Echoes the ID supplied in a requestScanCode response. A requested scan can accompany a repeat of the original event; it is not limited to a standalone scanCode event. Available by MplusKASSA v14.0.0.

scannedCode and codeType are omitted when unavailable or empty.

addSessionLine

{
    "addSessionLine": {
        "line": {
            "lineId": "c686f63d-46a7-498e-b421-c72e5cb7136b",
            "articleNumber": 1,
            "priceIncl": 2.5,
            "quantity": 1,
            "text": "Coffee"
        }
    }
}

Property	Type	Explanation
addSessionLine.line.lineId	string	The added line’s unique ID.
addSessionLine.line.articleNumber	bigint (optional)	The added line’s article number.
addSessionLine.line.priceIncl	number (optional)	The added line’s price including VAT.
addSessionLine.line.quantity	number (optional)	The added line’s quantity.
addSessionLine.line.text	string	The added line’s textual description.
On top of this the added line can also contain all the additional properties a session.lines[] object can contain.

updateSessionLine

{
    "updateSessionLine": {
        "line": {
            "lineId": "c686f63d-46a7-498e-b421-c72e5cb7136b",
            "articleNumber": 1,
            "priceIncl": 2.5,
            "quantity": 2,
            "text": "Coffee"
        }
    }
}

Property	Type	Explanation
updateSessionLine.line.lineId	string	The updated line’s unique ID.
updateSessionLine.line.articleNumber	bigint (optional)	The updated line’s article number.
updateSessionLine.line.priceIncl	number (optional)	The updated line’s price including VAT.
updateSessionLine.line.quantity	number (optional)	The updated line’s quantity.
updateSessionLine.line.text	string	The updated line’s textual description.
On top of this the updated line can also contain all the additional properties a session.lines[] object can contain.

removeSessionLine

{
    "removeSessionLine": {
        "line": {
            "lineId": "c686f63d-46a7-498e-b421-c72e5cb7136b",
            "articleNumber": 1,
            "priceIncl": 2.5,
            "quantity": 1,
            "text": "Coffee"
        }
    }
}

Property	Type	Explanation
removeSessionLine.line.lineId	string	The removed line’s unique ID.
removeSessionLine.line.articleNumber	bigint (optional)	The removed line’s article number.
removeSessionLine.line.priceIncl	number (optional)	The removed line’s price including VAT.
removeSessionLine.line.quantity	number (optional)	The removed line’s quantity.
removeSessionLine.line.text	string	The removed line’s textual description.
On top of this the removed line can also contain all the additional properties a session.lines[] object can contain.

mergeSession

{
    "mergeSession": {
        "mergeWithSessionId": "f232b716-8ab4-419e-b45e-e70720203e57"
    },
    "session": {
        "sessionId": "15a0ea55-3ae8-4191-a7c1-3e93984e23b4"
    }
}

Property	Type	Explanation
mergeSession.mergeWithSessionId	string	The session that the current session is merged with.
session.sessionId	string	The session that is merged.

moveSession

Added in MplusKASSA v60.8.0.

{
    "moveSession": {
        "moveFromTable": {
            "number": 2,
            "subNumber": 1
        },
        "moveToTable": {
            "number": 3,
            "subNumber": 1
        }
    }
}

Property	Type	Explanation
moveSession.moveFromTable	object	Source table.
moveSession.moveToTable	object	Destination table.
session.sessionId	uuid	The session being moved.

completeSession

{
    "completeSession": {
        "payments": [
            {
                "amount": 5,
                "description": "Contant",
                "method": "CONTANT"
            },
            {
                "amount": 10,
                "description": "Cadeaubon",
                "method": "CADEAUBON"
            }
        ]
    },
    "session": {
        "sessionId": "15a0ea55-3ae8-4191-a7c1-3e93984e23b4"
    }
}

Property	Type	Explanation
completeSession.payments[].amount	number	The amount that was paid with this specific payment method.
completeSession.payments[].description	string (optional)	The description label of this payment method.
completeSession.payments[].method	string	The reference id of this payment method.
The completeSession.payments list only contains the payments that were made in the final transaction, and does not include any previous prepayments that were made to the session. You can find a list of all (pre)payments in the session.payments list.

Property	Type	Explanation
completeSession.payments[].paymentId	uuid (optional)	Payment identifier, when supplied.

description is optional and omitted when empty. This payment structure is also used by session.payments, creditSession.payments and printBill.prepayments. Empty payment arrays may be absent.

creditSession

Available by MplusKASSA v11.1.13.

Contains the payments associated with a credit session.

{
    "creditSession": {
        "payments": [
            {
                "method": "CONTANT",
                "amount": -5.0
            }
        ]
    }
}

creditSession.payments is an optional array using the payment structure. Use the supplied amounts, including their signs.

printBill

Contains payments previously made to the bill.

{
    "printBill": {
        "prepayments": [
            {
                "method": "CONTANT",
                "amount": 5.0
            }
        ]
    }
}

printBill.prepayments is an optional array using the payment structure.

selectRelation

Added in MplusKASSA v43.1.1

{
    "selectRelation": {
        "relation": {
            "relationNumber": 1
        }
    }
}

Check the definition of session for possible contents of relation.

When a relation is deselected, the value of relation will be null.

customAction

{
    "customAction": {
        "customActionId": "A_CUSTOM_ACTION_ID",
        "buttonCaption": "The Button Caption",
        "onStartup": false,
        "longClick": false,
        "numpadValue": 1.5
    },
    "session": {
        "sessionId": "15a0ea55-3ae8-4191-a7c1-3e93984e23b4"
    }
}

Property	Type	Explanation
customAction.customActionId	text	The manually configured ID of the customAction button that was clicked.
customAction.buttonCaption	text	The manually configured caption of the customAction button that was clicked, can be changed through a webhook response.
customAction.onStartup	boolean	Whether or not the webhook was called during POS startup. You may use this to set initial state.
customAction.longClick	boolean (optional)	Whether or not the button was held for a long time. You may decide to alternate behaviour based on this. Available by MplusKASSA v59.3.0.
customAction.numpadValue	number (optional)	The current value of the POS numpad input.

Property	Type	Explanation
customAction.annotationId	string (optional)	Identifier of the annotation that triggered this custom action. See entityAnnotations. Added in MplusKASSA v68.0.0

course

Available by MplusKASSA v13.0.0.

Sent for kitchenStartCourse, kitchenCompleteCourse and kitchenServeCourse. These events can also include top-level order, tableOrder, cafeteriaOrder, table and relation objects when available.

{
    "course": {
        "courseNumber": 1,
        "name": "Starter",
        "abbreviation": "ST",
        "sequenceNumber": 1,
        "expectedPreparationTime": 600,
        "actualPreparationTime": 540
    }
}

Property	Type	Explanation
course.courseNumber	integer	Course number.
course.name	string	Course name.
course.abbreviation	string	Course abbreviation.
course.sequenceNumber	integer	Course sequence number.
course.expectedPreparationTime	integer (optional)	Expected preparation time in seconds. Available by MplusKASSA v13.0.0.
course.actualPreparationTime	integer (optional)	Actual preparation time in seconds. Available by MplusKASSA v13.0.0.

externalPayment

{
    "externalPayment": {
        "externalPaymentId": "7d5b3a3a-9330-11ed-a1eb-0242ac120002",
        "amount": 3.14,
        "method": "K_WEBHOOK",
        "callbackUrl": "https://yourplatform.example.com/callback"
    }
}

Property	Type	Explanation
externalPaymentId	string	Each external payment receives a new id.
amount	number	The amount that has to be paid.
method	string	The name of the payment method that was configured to trigger the webhook.
callbackUrl	string (optional)	If this URL is provided, please call it when you have the final status of the external payment. This is an important step in speeding up certain parts of the payment processing. You don’t need to do anything with the result of this request.
callbackUrl has been added in v56.0.0

Property	Type	Explanation
externalPayment.description	string (optional)	Description of the payment method; omitted when empty.

cafeteriaOrder

{
    "cafeteriaOrder": {
        "orderId": "8fdcaa6d-9908-4c16-b594-ee0f1ae10279",
        "year": 2019,
        "number": 13465,
        "ticketNumber": 465
    }
}

Property	Type	Explanation
cafeteriaOrder.orderId	uuid	Order identifier.
cafeteriaOrder.year	integer	Order numbering year.
cafeteriaOrder.number	64-bit integer	Order number.
cafeteriaOrder.ticketNumber	integer	Cafeteria ticket number.

tableOrder

{
    "tableOrder": {
        "orderId": "c7ec2390-9333-11ed-a1eb-0242ac120002",
        "year": 2023,
        "number": 1
    }
}

Property	Type	Explanation
tableOrder.orderId	uuid	Order identifier.
tableOrder.year	integer	Order numbering year.
tableOrder.number	64-bit integer	Order number.

order

{
    "order": {
        "orderId": "c7ec2390-9333-11ed-a1eb-0242ac120002",
        "year": 2023,
        "number": 1
    }
}

Property	Type	Explanation
order.orderId	uuid	Order identifier.
order.year	integer	Order numbering year.
order.number	64-bit integer	Order number.

table

{
    "table": {
        "number": 3,
        "subNumber": 1,
        "numberOfGuests": 2
    }
}

Property	Type	Explanation
table.number	integer	Table number.
table.subNumber	integer (optional)	Table subnumber.
table.tableName	string (optional)	Table name; omitted when empty. Available by MplusKASSA v10.0.3.
table.numberOfGuests	integer (optional)	Number of guests. Available by MplusKASSA v10.0.3.

The same object shape is used by session.table and both moveSession table objects.

determinePricing

Available by MplusKASSA v47.1.0.

Pricing event context, alongside the normal event, sender and available session. The serializer supports the fields below; values not supplied by the caller are explicitly null. There is no separate determinePricing response object; use the applicable standard response properties.

{
    "determinePricing": {
        "date": null,
        "timestamp": null,
        "pricegroup": null,
        "activity": null,
        "relation": null
    }
}

Property	Type	Explanation
determinePricing.date	date or null	Date-only string in YYYY-MM-DD format.
determinePricing.timestamp	datetime or null	ISO 8601 timestamp including timezone offset.
determinePricing.pricegroup	integer or null	Price group. The JSON spelling is exactly pricegroup.
determinePricing.activity	object or null	Activity context.
determinePricing.relation	object or null	Relation context.

dialog

When you reply with a dialog, the user will be able to select some dialog options. Afterwards, the same event will be sent to you again, but this time including the selected dialog options.

{
    "dialog": {
        "selectedDialogOptionIds": [
            1,
            2
        ]
    }
}

Property	Type	Explanation
dialog.selectedDialogOptionIds	string[] or integer[]	The ID’s of the selected dialog option. Can be zero, one or more.
On top of this, you also receive all the original data from the event.

Property	Type	Explanation
dialog.dialogId	string or integer (optional)	Echoes a nonempty dialog ID from the response. Available by MplusKASSA v14.0.0.

Use a consistent ID type for all dialog options; the implementation uses a shared integer-ID flag when serializing the selection. An empty selection may omit selectedDialogOptionIds.

form

Added in MplusKASSA v59

When you reply with a form, the user will be able to fill out and submit it. Afterwards, the same event will be sent to you again, but this time including the submitted form values.

{
    "form": {
        "id": "customer_registration",
        "cancelled": false,
        "fields": [
            {
                "id": "name",
                "value": "John Doe",
                "type": "text"
            },
            {
                "id": "email",
                "value": "john@doe.example.com",
                "type": "email"
            },
            {
                "id": "allergies",
                "selected": [
                    "peanut",
                    "gluten"
                ],
                "type": "select"
            }
        ]
    }
}

Property	Type	Explanation
form.id	string	Form identifier as specified in the initial form response.
form.cancelled	boolean	If the form was explicitly cancelled, this will be true.
form.fields[].id	string	Field identifier as specified in the initial form response.
form.fields[].value	string (optional)	No matter the original field type, submitted values are always sent as string.
form.fields[].selected	string[] (optional)	Contains the selected options in case of a select field.
On top of this, you also receive all the original data from the event.

Property	Type	Explanation
form.fields[].type	string	Field type, using the same names as in the form response.

form.cancelled is always serialized. value is optional; selected is only emitted when nonempty. The fields array can be absent when empty.

openUrl

Added in MplusKASSA v48.0.0

Contains preferences regarding usage of the openUrl response.

{
    "openUrl": {
        "redirectUrl": "https://mpluskassa.online/handheld/webhook/0f2e40a6-9336-11ed-a1eb-0242ac120002"
    }
}

Property	Type	Explanation
redirectUrl	string	If you plan to redirect the client to another URL during webhook interaction, please redirect back to this URL after completion.

error

{
    "error": {
        "code": "LINE_ALREADY_HAS_DISCOUNT",
        "message": "Line ID c686f63d-46a7-498e-b421-c72e5cb7136b already has a discount applied to it."
    },
    "original": {
        "event": {},
        "sender": {},
        "session": {}
    }
}

Property	Type	Explanation
error.code	string	One of the Error Codes.
error.message	string	Additional descriptive explanation of the cause of the error.
original	object	All of the details of the original event.

---

Response objects

error

{
    "error": {
        "code": "INVALID_SUBSCRIPTION_ID",
        "message": "The supplied subscription does not exist in our database. Please contact support at ... to set-up your account."
    }
}

Property	Type	Explanation
error.code	string	One of the Error Codes.
error.message	string	Additional descriptive explanation of the cause of the error.

scanCode

{
    "scanCode": {
        "recognized": true,
        "relationNumber": 123
    }
}

Property	Type	Explanation
scanCode.recognized	boolean	Did you recognize the code or not? If you respond with true, the POS will stop looking for the code in its own data.
scanCode.relationNumber	int (optional)	A relation to select in the POS.

lineChanges

{
    "lineChanges": [
        {
            "lineId": "c686f63d-46a7-498e-b421-c72e5cb7136b",
            "externalDiscount": {
                "discountId": "12551430-7ce9-11e7-bb31-be2e44b06b34",
                "applyToQuantity": 1,
                "discountPercentage": 50,
                "discountAmount": 1,
                "discountDescription": "Sample Voucher",
                "discountType": "promotional"
            }
        }
    ]
}

Property	Type	Explanation
lineChanges[].lineId	uuid	The UUID of the session line that you want to change.
lineChanges[].externalDiscount	externalDiscount (optional)	The details of an external discount are explained below.
externalDiscount.discountId	uuid	This is a UUID you generate and store to remember that you applied this discount.
externalDiscount.discountPercentage	number (optional)	The discount percentage that you want to apply to the line.
externalDiscount.applyToQuantity	number (optional)	The quantity of this line that you want to apply the discount too. For example, if the quantity of the line is 2, but you want to apply the discount to 1 of these 2.
externalDiscount.discountAmount	number (optional)	The exact discount amount that you want to apply to the line.
externalDiscount.discountDescription	string (optional)	A descriptive label for the discount.
externalDiscount.discountType	string (optional)	Can be any kind of text, will be usable as a filter in reports Available by MplusKASSA v58.0.0.

Only external-discount changes are parsed here; arbitrary changes to price, text or quantity are not supported by lineChanges. Discount percentages must be between 0 and 100. applyToQuantity defaults to 1 for quantity validation, must have the same sign as the line quantity, and combined applications to the same line must not exceed its quantity. Existing discounts and discounts owned by another consumer are subject to configuration restrictions.

Implementation limitation: externalDiscount: null is recognized internally as deletion, but the current line parser does not propagate it as a completed discount response. Do not rely on null to remove a discount in this checkout.

lineAdditions

{
    "lineAdditions": [
        {
            "lineId": "f1b8a9aa-9875-11e7-abc4-cec278b6b50a",
            "extLineId": "foobar-123",
            "articleNumber": 1005,
            "barcode": "8712345678901",
            "pluNumber": "9864",
            "supplierArticleNumber": "XR-123",
            "extArticleId": "651",
            "priceIncl": 2.1,
            "quantity": 3,
            "text": "Chocolate Milk",
            "externalDiscount": {
                "discountId": "d2091980-7e7d-11e7-bb31-be2e44b06b34",
                "discountPercentage": 10
            }
        }
    ]
}

Property	Type	Explanation
lineAdditions[].lineId	uuid (optional)	The UUID of the session line that you want to add. You are allowed to generate this. If you omit this an UUID will be generated automatically, but it will be more difficult for you to know which line you added.
lineAdditions[].extLineId	string (optional)	An identifier so you can recognize this line in a later stage.
lineAdditions[].articleNumber	bigint (optional)	This number should be present in the MplusKASSA administration.
lineAdditions[].barcode	string (optional)	This barcode should be present in the MplusKASSA administration.
lineAdditions[].pluNumber	string (optional)	This PLU number should be present in the MplusKASSA administration.
lineAdditions[].supplierArticleNumber	string (optional)	This supplier article number should be present in the MplusKASSA administration.
lineAdditions[].extArticleId	string (optional)	This external article ID should be present in the MplusKASSA administration.
You can add an article through articleNumber, barcode, pluNumber, supplierArticleNumber, extArticleId, or a combination thereof.
lineAdditions[].priceIncl	number (optional)	The line’s price including VAT. If you omit this, the default price will be used.
lineAdditions[].quantity	number (optional)	The line’s quantity (how many). If you omit this, a default quantity of 1 will be used.
lineAdditions[].text	string (optional)	The line’s text (description). If you omit this, the default article text will be used.
You can add a simple text line (without any article references) by using only text.
lineAdditions[].externalDiscount	externalDiscount (optional)	See the explanation at session for more details.

Property	Type	Explanation
lineAdditions[].vatCode	integer (optional)	VAT code accepted by the response parser; application depends on the receiving line-addition handler.
lineAdditions[].vatPercentage	number (optional)	VAT percentage accepted by the parser, rounded to two decimals; application depends on the receiving handler.

articleNumber also accepts a decimal integer string. priceIncl and quantity accept numeric strings, but JSON numbers are recommended. Prices are rounded to two decimals and quantities to ten. For an external discount, use the response definition in lineChanges, including discountId.

lineDeletions

{
    "lineDeletions": [
        {
            "lineId": "f1b8a9aa-9875-11e7-abc4-cec278b6b50a"
        }
    ]
}

Property	Type	Explanation
lineDeletions[].lineId	uuid	The UUID of the session line that you want to delete.
It is possible that your request for deletion will be denied. For example, you can only delete lines that you yourself added. You will receive an error message if this is the case.
Since v11.3.0 this behaviour depends on the setting “Webhooks mogen alle regels verwijderen”.

lockSession

Added in MplusKASSA v11.1.0

{
    "lockSession": true
}

Property	Type	Explanation
lockSession	boolean	Locks or unlocks the session from further changes.

lockSessionForAdditions

Added in MplusKASSA v16.2.0

{
    "lockSessionForAdditions": true
}

Property	Type	Explanation
lockSessionForAdditions	boolean	Locks or unlocks the session from further additions (deletions/decreases are allowed).

receiptFooter

A top-level receiptFooter is handled for completeSession. The wrapper completeSession.receiptFooter is also accepted. External-payment responses can supply their own nested footers; see externalPayment.

{
    "receiptFooter": {
        "textBefore": "Thank you!\nPlease visit again.",
        "barcode": {
            "codeType": "qrcode",
            "code": "https://example.com/receipt"
        },
        "textAfter": "Your receipt reference",
        "printSeparate": false
    }
}

Use an array of these objects for multiple footers.

Property	Type	Explanation
textBefore	string (optional)	Text before the barcode. text and message are also accepted. Newlines are supported.
barcode	object (optional)	Barcode to print. Null means no barcode.
barcode.codeType	string (optional)	code128 (default) or qrcode.
barcode.code	string	Barcode contents; code128: 1–48 characters; qrcode: 1–2953 characters.
textAfter	string (optional)	Text after the barcode. Available by MplusKASSA v21.2.1.
printSeparate	boolean (optional)	Print separately, with a cut between receipt and footer; defaults to false.

The pre-barcode text is limited to 10,000 characters by footer validation. Receipt layout configuration must support webhook footers.

Implementation limitation: the supplied documentation listed textBeforeOptions and textAfterOptions for alignment, size, underline and bold. The current webhook footer parser does not read these objects; they are not supported by this JSON path.

billFooter

Added in MplusKASSA v16.2.0

Attention: billFooter only works with the printBill event.

The JSON details of billFooter are identical to receiptFooter.

The printBill.billFooter wrapper is also accepted. The same formatting limitations and footer validation rules apply.

dialog

{
    "dialog": {
        "required": false,
        "requireConfirmation": true,
        "allowMultipleOptions": false,
        "dialogTitle": "Select the voucher to apply",
        "columns": 2,
        "dialogOptions": [
            {
                "optionId": 1,
                "optionName": "Second cup of coffee for free!",
                "optionColor": "#00ff00"
            },
            {
                "optionId": 2,
                "optionName": "5% discount over the entire order"
            },
            {
                "optionId": 3,
                "optionName": "Coffee + Cake 3,-"
            }
        ]
    }
}

Property	Type	Explanation
dialog.required	boolean	Is a choice required?
dialog.allowMultipleOptions	boolean	Is more than one choice allowed?
dialog.dialogTitle	string	Which title should the dialog show?
dialog.columns	int (optional)	How many columns should the dialog use to display the options?
dialog.dialogOptions[].optionId	string or integer	The option’s ID; use one consistent ID type within the dialog.
dialog.dialogOptions[].optionName	string	The option’s textual description.
dialog.dialogOptions[].optionColor	string (optional)	The option’s color in hexadecimal format.
requireConfirmation was added in v46
dialog.requireConfirmation	boolean (optional)	Do you need to click confirm after selecting an option? Useful to prevent misclicks.

Property	Type	Explanation
dialog.dialogId	string or integer (optional)	Identifier echoed in the follow-up request. Available by MplusKASSA v14.0.0.
dialog.dialogOptions[].disabled	boolean (optional)	Prevents selection; defaults to false. Available by MplusKASSA v59.3.0.
dialog.dialogOptions[].enabled	boolean (optional)	Inverse of disabled. Supply only one of these flags. Available by MplusKASSA v59.3.0.
dialog.dialogOptions[].image	string (optional)	Image reference for the option; rendering depends on the client. Available by MplusKASSA v59.3.2.

required, allowMultipleOptions and requireConfirmation default to false. Use six-digit RGB hex colors such as #00ff00. Article lookup properties are parsed for form options, but not for dialog options in this checkout.

form

Added in MplusKASSA v59

{
    "form": {
        "id": "customer_registration",
        "title": "Register New Customer",
        "enableReset": true,
        "fields": [
            {
                "id": "name",
                "type": "text",
                "required": true,
                "label": "Your name",
                "hint": "Use your official name",
                "value": "John",
                "minimumLength": 1,
                "maximumLength": 200
            },
            {
                "type": "label",
                "value": "Just some information",
                "separator": "below"
            },
            {
                "id": "email",
                "type": "email"
            },
            {
                "id": "card_number",
                "type": "text",
                "regex": "^C\\d{8}$"
            },
            {
                "id": "family_size",
                "type": "number",
                "decimals": 0,
                "minimumValue": 1,
                "maximumValue": 9
            },
            {
                "id": "allergies",
                "type": "select",
                "multiple": true,
                "columns": 3,
                "options": [
                    {
                        "id": "peanut",
                        "label": "Peanuts",
                        "color": "#a52a2a",
                        "selected": false,
                        "image": "https://mpluskassa.nl/images/peanut.png"
                    },
                    {
                        "id": "gluten",
                        "label": "Gluten",
                        "color": "#00ff00",
                        "selected": true
                    }
                ]
            },
            {
                "id": "welcome_gift",
                "type": "select",
                "multiple": false,
                "columns": 2,
                "options": [
                    {
                        "id": "gift_01",
                        "label": "Peanuts",
                        "articleNumber": "2343241"
                    },
                    {
                        "id": "gift_02",
                        "label": "Gluten",
                        "articleNumber": "2136533",
                        "disabled": true
                    }
                ]
            },
            {
                "id": "start_of_contract",
                "type": "date"
            },
            {
                "id": "preferred_delivery_time",
                "type": "time"
            },
            {
                "id": "accept_terms",
                "type": "checkbox",
                "label": "I accept the Terms and Conditions"
            }
        ]
    }
}

Property	Type	Explanation
form.id	string	Form identifier that will be included when the form is submitted.
form.title	string	Title will be displayed above the form.
form.enableReset	boolean (optional)	Whether to display the button that will reset the form to its original state.
form.fields[].id	string	Field identifier that will be included when the form is submitted.
form.fields[].type	string	text, email, password, postalcode, number, date, time, datetime, select, checkbox, label, postaladdress
form.fields[].required	boolean	Whether the field is required.
form.fields[].separator	string (optional)	none, above, below Available by MplusKASSA v59.3.0.
form.fields[].label	string	What caption to display with the form field.
form.fields[].hint	string (optional)	A longer explanation to clarify the requirements.
form.fields[].value	string (optional)	A default value to populate the field with.
form.fields[].minimumLength	int (optional)	A minimum required text length.
form.fields[].maximumLength	int (optional)	Maximum permitted text length.
form.fields[].regex	string (optional)	A regex pattern to validate the input.
form.fields[].decimals	int (optional)	How many decimals to allow on a number field.
form.fields[].minimumValue	number (optional)	Minimum value of a number field.
form.fields[].maximumValue	number (optional)	Maximum value of a number field.
form.fields[].multiple	boolean (optional)	Whether to allow multiple selections on a select field.
form.fields[].columns	integer (optional)	How many columns to use to display the select options.
form.fields[].options[].id	string	Option identifier that will be included when the form is submitted.
form.fields[].options[].label	string	The label that will be display on the option.
form.fields[].options[].color	string (optional)	Six-digit RGB hexadecimal color (with optional #) that will be used as background color.
form.fields[].options[].selected	boolean (optional)	Whether the option should already be selected.
form.fields[].options[].image	string (optional)	This image will be shown on the option.
image was added in v59.3.2
form.fields[].options[].articleNumber	string (optional)	Will enrich the option button with article information and imagery from the POS system.
form.fields[].options[].barcode	string (optional)	Article lookup reference; client support varies.
form.fields[].options[].pluNumber	string (optional)	Article lookup reference; client support varies.
form.fields[].options[].supplierArticleNumber	string (optional)	Article lookup reference; client support varies.
form.fields[].options[].extArticleId	string (optional)	Article lookup reference; client support varies.
form.fields[].options[].disabled	boolean (optional)	Can be used to show an option that is not selectable.
disabled was added in v59.3.2

Additional form properties

Field types password and datetime: available by v59.0.1. Field types label, postalcode and postaladdress: available by v59.3.0.

Property	Type	Explanation
form.submitText	string (optional)	Custom submit-button caption. Available by MplusKASSA v59.0.1.
form.cancelText	string (optional)	Custom cancel-button caption. Available by MplusKASSA v59.3.0.
form.fields[].prefix	string (optional)	Parsed prefix; client support varies. Available by MplusKASSA v59.0.1.
form.fields[].suffix	string (optional)	Recognized, but currently assigned to the prefix member by the parser. Do not rely on suffix behavior. Available by MplusKASSA v59.0.1.
form.fields[].allowNegative	boolean (optional)	Allow negative numeric input. Available by MplusKASSA v59.0.1.
form.fields[].color	string (optional)	Six-digit RGB hexadecimal field color, with optional #. Available by MplusKASSA v59.0.1.
form.fields[].futureOnly	boolean (optional)	Parsed future-date constraint; see client limitations below. Available by MplusKASSA v59.0.1.
form.fields[].pastOnly	boolean (optional)	Parsed past-date constraint; see client limitations below. Available by MplusKASSA v59.0.1.
form.fields[].earliestDate	string (optional)	Parsed using the POS locale date parser, not an ISO 8601 timestamp parser. Available by MplusKASSA v59.0.1.
form.fields[].latestDate	string (optional)	Parsed using the POS locale date parser, not an ISO 8601 timestamp parser. Available by MplusKASSA v59.0.1.
form.fields[].sunday	object (optional)	Sunday schedule; fields below. Available by MplusKASSA v59.0.1.
form.fields[].monday	object (optional)	Monday schedule. Available by MplusKASSA v59.0.1.
form.fields[].tuesday	object (optional)	Tuesday schedule. Available by MplusKASSA v59.0.1.
form.fields[].wednesday	object (optional)	Wednesday schedule. Available by MplusKASSA v59.0.1.
form.fields[].thursday	object (optional)	Thursday schedule. Available by MplusKASSA v59.0.1.
form.fields[].friday	object (optional)	Friday schedule. Available by MplusKASSA v59.0.1.
form.fields[].saturday	object (optional)	Saturday schedule. Available by MplusKASSA v59.0.1.
form.fields[].options[].enabled	boolean (optional)	Inverse of disabled; supply only one flag. Available by MplusKASSA v59.3.0.

Each weekday object accepts available (boolean, default true), fromHour, fromMinute, throughHour and throughMinute (optional integers). These properties are directly on the field, not inside calendar or number wrappers.

form.enableReset and field required default to false. Form field and option IDs are strings. Option articleNumber accepts an integer or decimal integer string; barcode, pluNumber, supplierArticleNumber and extArticleId are strings.

Client limitations: the current desktop form adapter forwards weekday availability, but not the schedule time ranges, futureOnly, pastOnly, earliest/latest dates or prefix/suffix. Its option conversion forwards ID, label, color and disabled status, but not article/image enrichment or preselection. These fields may be parsed without taking effect in that desktop path. Validate behavior on the target client.

message

{
    "message": [
        {
            "message": "We encountered a situation that requires your attention",
            "customerMessage": "ATTENTION REQUIRED",
            "displayTime": 5,
            "messageDisplayTime": 5,
            "customerMessageDisplayTime": 15,
            "hideTimestamp": false,
            "clearScreen": true,
            "clearCustomerScreen": true,
            "monospacedFont": true,
            "backgroundColor": "#ff0000"
        }
    ]
}

The message property accepts one message object or an array for multiple messages.
Property	Type	Explanation
message[].message	text (optional)	Show a message on the POS user’s display.
message[].customerMessage	text (optional)	Show a message on the POS customer display.
message[].displayTime	int (optional)	This will ensure the message and customerMessage are shown for at least this amount of seconds.
message[].messageDisplayTime	int (optional)	This will ensure the message is shown for at least this amount of seconds.
message[].customerMessageDisplayTime	int (optional)	This will ensure the customerMessage is shown for at most this amount of seconds.
message[].hideTimestamp	boolean (optional)	When set to true, this will hide the timestamps that are usually shown in front of the messages.
message[].clearScreen	boolean (optional)	When set to true, this will clear all previous messages.
message[].clearCustomerScreen	boolean (optional)	When set to true, this will clear the current customer message.
message[].monospacedFont	boolean (optional)	When set to true, this will display the messages in a monospaced font so you can better align multiple lines.
message[].backgroundColor	string (optional)	The background color of the message popup in hexadecimal format. Or preset color names, like “red” and “green”. Available by MplusKASSA v22.2.0.

message and messages both accept one message object or an array. Display times are clamped: operator messages to 0–10 seconds, customer messages to 0–60 seconds. displayTime supplies both durations; explicit per-screen durations take precedence. Preset background colors recognized by the parser are red, green, error, success and alert; otherwise use six-digit RGB hex. Boolean message flags default to false. The same message properties can be embedded in scanCode, polling and externalPayment.

requestScanCode

Added in MplusKASSA v13.1.0

{
    "requestScanCode": {
        "required": true,
        "requestTitle": "Please scan your code now",
        "requestId": 1
    }
}

Property	Type	Explanation
requestScanCode.required	boolean	Is a scan required?
requestScanCode.requestTitle	string	What would you like the POS screen to display to the user?

Property	Type	Explanation
requestScanCode.requestId	integer	Supply an ID to correlate the next scan through scanCode.requestId.

required defaults to true. requestScanCode is rejected as a response to the standalone scanCode event.

displayBarcode

Added in MplusKASSA v21.2.0

{
    "displayBarcode": {
        "codeType": "qrcode",
        "code": "https://example.com/loremipsum"
    }
}

Property	Type	Explanation
displayBarcode.codeType	string (optional)	Code type, for example code128 or qrcode; support depends on the display client.
displayBarcode.code	string	The contents of the barcode

Property	Type	Explanation
displayBarcode.text	string (optional)	Text displayed alongside the code; message is also accepted.

codeType defaults to code128. Actual display support depends on the client; the parser does not validate display code types. displayQrcode is a legacy alias for the response property and does not change the default code type.

hideBarcode

Added in MplusKASSA v21.2.0

{
    "hideBarcode": true
}

Property	Type	Explanation
hideBarcode	boolean	Instantly hide a code that is currently displayed.

The current parser acts on the presence of hideBarcode, regardless of its boolean value. Omit the property when you do not want to hide the code. hideQrcode is an alias. If both display and hide are supplied, hide takes precedence.

openUrl

Added in MplusKASSA v48.0.0

{
    "openUrl": {
        "url": "https://payment-platform.example.com/transaction/123",
        "autoOpen": false,
        "urlTitle": "Click here to start payment",
        "closeOnDomainChange": true,
        "minimumWidth": 800,
        "minimumHeight": 500
    }
}

Property	Type	Explanation
url	text	The actual URL to open.
autoOpen	boolean (optional)	Whether or not to automatically open the URL.
urlTitle	text (optional)	The title of the link/button in case the URL is not set to open automatically, or is unable to open automatically.
closeOnDomainChange	boolean (optional)	Set this if you want the browser component to automatically close when the current domain changes, e.g. from payment-platform.example.com to some-other-domain.com. Available by MplusKASSA v47.1.0.
minimumWidth	int (optional)	In case of a browser popup, determines the minimum width the popup should receive. Available by MplusKASSA v48.1.2.
minimumHeight	int (optional)	In case of a browser popup, determines the minimum height the popup should receive. Available by MplusKASSA v48.1.2.

polling

Added in MplusKASSA v11.3.0

{
    "polling": {
        "finished": false,
        "message": "The process has been completed for 55%",
        "customerMessage": "Progress: 55%",
        "displayTime": 5,
        "messageDisplayTime": 5,
        "customerMessageDisplayTime": 15,
        "hideTimestamp": false,
        "clearScreen": true,
        "clearCustomerScreen": true,
        "monospacedFont": true
    }
}

Property	Type	Explanation
polling.finished	boolean	Tell MplusKASSA whether the polling process is finished or not. When you return false, MplusKASSA schedules another request using the configured polling interval.
polling.message	text (optional)	Show a message on the POS user’s display. Use this to update the user on progress made in the polling process.
polling.customerMessage	text (optional)	Show a message on the POS customer display. Use this to update the customer on progress made in the polling process.
polling.displayTime	int (optional)	This will ensure the message and customerMessage are shown for at least this amount of seconds.
polling.messageDisplayTime	int (optional)	This will ensure the message is shown for at least this amount of seconds.
polling.customerMessageDisplayTime	int (optional)	This will ensure the customerMessage is shown for at most this amount of seconds.
polling.hideTimestamp	boolean (optional)	When set to true, this will hide the timestamps that are usually shown in front of the messages.
polling.clearScreen	boolean (optional)	When set to true, this will clear all previous messages.
polling.clearCustomerScreen	boolean (optional)	When set to true, this will clear the current customer message.
polling.monospacedFont	boolean (optional)	When set to true, this will display the messages in a monospaced font so you can better align multiple lines.

finished defaults to false. Polling also accepts backgroundColor and the other shared message properties.

For backgroundPoll, a response containing requestCustomAction, externalCardScan, prepayTable or entityAnnotations implicitly ends the current poll if no explicit polling object is present. The background thread then starts a fresh request with a new event counter. Explicit polling instructions take precedence.

The desktop dispatcher applies a delay bounded to 10–3000 milliseconds. Polling without an explicit polling or external-payment response uses at least a one-second interval. Successful or cancelled external payments can terminate polling independently. MplusQservice does not perform these automatic retries: its API client must drive continuation.

customActionChange

Added in MplusKASSA v15.1.0

{
    "customActionChange": {
        "customActionId": "STATUS_BUTTON",
        "buttonCaption": "Current status: ON"
    }
}

Property	Type	Explanation
customActionChange.customActionId	text	The ID of the customAction button that should be changed.
customActionChange.buttonCaption	text	The desired new caption for the customAction button.

vatMethodChange

Added in MplusKASSA v15.1.0

{
    "vatMethodChange": "shifted"
}

Property	Type	Explanation
vatMethodChange	text	inclusive, exclusive, shifted

externalCardScan

Notify the POS that an external card was scanned, that the POS should know about.

Added in MplusKASSA v16.2.0

{
    "externalCardScan": {
        "cardIdentifier": "b4a7689d-4332-4b94-9f97-1dce8dcdca64",
        "cardDescription": "My Special Card",
        "cardBalance": 76.5,
        "cardExpiration": "2019-12-31",
        "cardBlocked": false,
        "displayTime": 5,
        "isNewBalance": false
    }
}

Property	Type	Explanation
externalCardScan.cardIdentifier	text (optional)	Use any kind of string that you use as identifier for this card within your system. Does not need to be present within the POS.
externalCardScan.cardDescription	text (optional)	Enter the name of the card owner, or a description of the card itself.
externalCardScan.cardBalance	number (optional)	The card’s current balance.
externalCardScan.cardExpiration	datetime (optional)	The date and time when the card expires and is no longer usable. Please note that we do not actually do anything with this date, it is only used for informational purposes in the POS.
externalCardScan.cardBlocked	boolean (optional)	When set to true the POS will indicate on screen that the card is blocked.
externalCardScan.displayTime	int (optional)	You can use this to influence the time until the card details should be hidden again. This overrides the setting in the POS itself. Set to 0 to keep the details on screen until the next receipt.
externalCardScan.isNewBalance	boolean (optional)	When set to true the POS will interpret the balance card as being the balance after the transaction and display accordingly.
Even though all properties are optional, nothing will be displayed on the POS if you omit them all.

displayTime is clamped to 0–60 seconds. Card balances are rounded to two decimals. Invalid expiration text produces INVALID_DATA; this path uses a legacy ISO 8601 parser, so do not infer the timezone guarantees of annotation timestamps from this field.

prepayTable

Added in MplusKASSA v16.2.0

{
    "prepayTable": {
        "table": {
            "number": 20,
            "subNumber": 1
        },
        "sessionId": "367ef280-1b67-11ea-978f-2e728ce88125",
        "payments": [
            {
                "paymentId": "af282ee3-c516-4805-96c1-fd9aed75f330",
                "amount": 14.99,
                "method": "MY_PAYMENT_METHOD"
            }
        ]
    }
}

Property	Type	Explanation
prepayTable.table.number	int	Designate the table’s number that the payments are meant for.
prepayTable.table.subNumber	int (optional)	Designate the table’s subnumber that the payments are meant for.
prepayTable.sessionId	uuid	Provide the session ID of the table.
prepayTable.payments[].paymentId	uuid	Provide a unique ID, the POS will use to make sure this payment is not registered more than once.
prepayTable.payments[].amount	number	The amount that was paid.
prepayTable.payments[].method	string	Required nonempty payment-method reference. It must be valid for this webhook consumer.

payments accepts an array or one payment object. Every parsed payment requires a non-null paymentId, a nonempty method, and a nonzero amount. There is no omitted-method fallback in the current parser.

requestCustomAction

Added in MplusKASSA v17.0.0

{
    "requestCustomAction": {
        "customActionId": "A_CUSTOM_ACTION_ID"
    }
}

Property	Type	Explanation
requestCustomAction.customActionId	text	The manually configured ID of the customAction button that you would like to trigger.
It is important to realize that this is a request to trigger the custom action, not a guarantee that it will. Reasons why the custom action may not trigger are: (1) the POS is not running, (2) the POS is currently in an interrupted state (like processing an electronic payment), (3) the POS currently has no logged in user or (4) the POS is currently in a blocked state (like displaying a dialog).

version

Added in MplusKASSA v23.0.0

{
    "version": "2.4"
}

Property	Type	Explanation
version	text	A string representing the version of your software (or the version of the Webhook middleware you created).
This version number will be added to the communication log and can help with debugging version-related problems.

The recorded string is truncated to 255 characters. externalVersion is an accepted alias.

externalPayment

Influence the currently running external payment.

{
    "externalPayment": {
        "externalPaymentId": "7a4d4fe3-1234-4567-89ab-5fc2fd596b26",
        "started": false,
        "confirmed": false,
        "cancelled": false,
        "finalAmount": 20,
        "externalTransactionReference": "KQUA6JcQ7sW5qgTXpCYXx4Lr",
        "receiptTexts": [
            {
                "type": "cardholder",
                "text": "TRANSACTION DETAILS\nTO PRINT\nON THE RECEIPT"
            },
            {
                "type": "merchant",
                "text": "COPY FOR THE MERCHANT\nNEEDS CARDHOLDER SIGNATURE",
                "requiresSignature": true
            }
        ],
        "cardType": "Maestro",
        "terminalId": "87420312",
        "method": "My Payment Platform",
        "requiresReceiptPrinter": true,
        "messages": [
            {
                "message": "Payment ready to be started",
                "customerMessage": "Please insert EUR 11.25",
                "hideTimestamp": false,
                "monospacedFont": false,
                "clearScreen": false,
                "clearCustomerScreen": false,
                "messageDisplayTime": 3,
                "customerMessageDisplayTime": 3,
                "backgroundColor": "#ff0000"
            }
        ]
    }
}

Property	Type	Explanation
externalPaymentId	uuid	The external payment ID as received from the POS in the first place. So the POS can verify you are talking about the same payment.
started	boolean (optional)	Has the external payment process been started? The external payment flow won’t progress from the start, to poll stage until you respond TRUE.
confirmed	boolean (optional)	Has the external payment process been successfully completed? The payment flow will end and the payment will be registered after you respond TRUE to this.
cancelled	boolean (optional)	Has the external payment process been cancelled/aborted/failed? The payment flow will end and the payment will be not be registered after you respond TRUE to this.
finalAmount	number (optional)	When the external payment succeeds, but with a differing amount than requested, you can specify the actual final amount through this variable. This requires activation of the software setting Webhooks > Algemeen > Webhooks mogen het via hen betaalde bedrag aanpassen.

Added in MplusKASSA v48.0.0

externalTransactionReference	string (optional)	Use this to assign a reference to the external transaction, which will be stored with the POS payment.
receiptTexts[].type	string (optional)	cardholder (default), merchant. Use this to tell the POS for whom the receipt is intended.
receiptTexts[].text	string	The actual text to print on the receipt.
receiptTexts[].requiresSignature	boolean (optional)	When this is true, the POS will prompt the merchant to have the cardholder sign this receipt.
cardType	string (optional)	Use this to store the used card type with the payment, e.g. Maestro or VPAY. This may be used by the POS to group payments.
terminalId	string (optional)	Use this to store a terminal ID with the payment, which may be used by the POS to group payments.
method	string (optional)	Use this to store which payment method was used externally.
requiresReceiptPrinter	boolean (optional)	Use this in the startExternalPayment response to let us know a configured printer is a requirement for a successful transaction. Available by MplusKASSA v50.0.2.
For an explanation of all the remaining message-related properties, please see message.

Property	Type	Explanation
externalPayment.receiptFooters	object or array (optional)	Receipt footers to retain with an external payment, using the receiptFooter structure. Supply them with the final confirmed: true or cancelled: true response. Available by MplusKASSA v61.0.0.
externalPayment.messages	object or array (optional)	Shared message object(s). A nested message object/array replaces messages parsed directly from the payment object.

receiptFooter, footer and footers are aliases for receiptFooters. Null external-payment properties are skipped. Empty receipt texts are omitted; receipt type defaults to cardholder and requiresSignature defaults to false. Final amounts are rounded to two decimals. Whether an adjusted amount may be lower or higher is checked separately by the payment flow. Send a valid body for startExternalPayment and echo the matching externalPaymentId.

entityAnnotations

Added in MplusKASSA v68.0.0

Sets annotations for one or more entities. This response accepts a single object or an array of objects. Each item replaces the complete annotation list owned by the responding webhook consumer for that exact entity; it does not merge by annotation ID. Other consumers’ annotation sets are retained. Send annotations: [] to remove your set. Omitting annotations also produces an empty list, so always include it explicitly.

{
    "entityAnnotations": [
        {
            "entity": {
                "type": "TABLE",
                "branchNumber": 1,
                "tableNumber": 20,
                "tableSubNumber": 0
            },
            "annotations": [
                {
                    "id": "reservation-123",
                    "text": "Reservation for Alice, party of four",
                    "badge": "18:30",
                    "customActionId": "OPEN_RESERVATION",
                    "scheduledAt": "2026-09-22T18:30:00+02:00",
                    "expiresAt": "2026-09-22T22:00:00+02:00"
                }
            ]
        }
    ]
}

Property	Type	Explanation
entity	object	Required entity identifier; shapes below.
annotations	array	Complete replacement list for this entity and consumer. A non-array value is rejected.
annotations[].id	string	Nonempty identifier. Entries without it are ignored when displayed.
annotations[].text	string	Nonempty display text. Entries without it are ignored when displayed.
annotations[].badge	string (optional)	Short badge text.
annotations[].icon	string (optional)	Icon name in the POS icon collection, not an arbitrary URL. Displayed only if that icon exists.
annotations[].customActionId	string (optional)	Custom action associated with the annotation. Activation can send customAction.annotationId containing this annotation’s id.
annotations[].scheduledAt	datetime (optional)	ISO 8601 datetime with timezone offset, parsed with the timezone-aware helper. Used for scheduling/order indication; it is not a delayed webhook trigger.
annotations[].expiresAt	datetime (optional)	ISO 8601 datetime with timezone offset. Expired annotations are excluded when read for display.

The consumer ID is taken from the current webhook configuration; do not supply a different webhookConsumerId to select an owner. The store accepts the JSON array, while the display reader skips non-object entries and entries lacking string id or text. Invalid or non-string timestamps are treated as absent, so validate them before sending. The table UI displays table annotations; accepting another entity type does not imply every screen displays its annotations.

Entity identifiers

entity.type is a case-sensitive enum string. Entity property names may use lower camel case as below; the parser uppercases their first character before passing them to the entity decoder.

entity.type	Required identifier properties
TABLE	branchNumber (positive integer), tableNumber and tableSubNumber (integers identifying a valid table).
ORDER, INVOICE	uuid plus version (positive integer or -1 for the latest-version sentinel).
RECEIPT, PROPOSAL, CONTRACT, PACKING_SLIP	uuid.
PURCHASE_ORDER, PURCHASE_DELIVERY, INTERBRANCH_ORDER, INTERBRANCH_SHIPMENT	yearNumber string in the administration’s year/number representation.
INTERBRANCH_DELIVERY	yearSubNumber string in the administration’s year/number/subnumber representation.

Supply exactly the identifier shape matching the type. A reference string fallback exists in the decoder but does not satisfy validation for the entity types above. The latest-version sentinel is accepted as an identifier; annotation storage uses the serialized identifier as the key and does not resolve it to a concrete document version.

Accepted response aliases

Use the property names shown in the main reference for new integrations. The parser also accepts the spellings below in their corresponding object context. Aliases are case-sensitive and are not global substitutions. For example, id means different things inside a dialog, line or payment. Supply one spelling per property; conflicting aliases have parser-order-dependent behavior. These aliases apply to responses, not to the request fields emitted by the POS.

Property/context	Accepted spellings
line changes	lineChanges, changes
line additions	lineAdditions, additions
line deletions	lineDeletions, deletions
lock session	lockSession, lock
lock session for additions	lockSessionForAdditions, lockForAdditions, lockAdditions
messages	messages, message
relation number	relationNumber, relation
receipt footer	receiptFooter, receiptFooters, footer, footers
bill footer	billFooter, billFooters, receiptFooter, receiptFooters, footer, footers
session id	sessionId, id
line id	lineId, id
discount id	discountId, id
article number	articleNumber, article, number
line text	lineText, text, lineDescription, description
price incl	priceIncl, price
plu number	pluNumber, plu
ext article id	extArticleId, externalArticleId
ext line id	extLineId, externalLineId
apply to quantity	applyToQuantity, quantity
discount percentage	discountPercentage, percentage
discount amount	discountAmount, amount
discount description	discountDescription, description, text
table number	tableNumber, number
table sub number	tableSubNumber, subNumber, sub
payments	payments, payment
barcode type	barcodeType, codeType, type
payment id	paymentId, id
payment amount	paymentAmount, amount
payment method	paymentMethod, method
external payment id	externalPaymentId, id
started	started, start
confirmed	confirmed, confirm
cancelled	cancelled, canceled, cancel
final amount	finalAmount, final
external transaction reference	externalTransactionReference, extTransactionRef, transactionReference, transactionRef, externalTransaction, extTransaction, externalTransactionId, extTransactionId
receipt texts	receiptTexts, receiptText, receipt, texts
card type	cardType, card
terminal id	terminalId, extTerminalId
external method	externalMethod, extMethod, method
requires signature	requiresSignature, signatureRequired
allow multiple options	allowMultipleOptions, allowMultiple, multiple
require confirmation	requireConfirmation, confirmationRequired, confirm
columns	columns, cols
dialog id	dialogId, id
form id	formId, id
enable reset	enableReset, reset, enableClear, clear
cancel text	cancelText, cancel
submit text	submitText, submit
dialog or form title	dialogTitle, title, dialogName, name, dialogText, text, formTitle
dialog options	dialogOptions, options
form fields	formFields, fields
option id	optionId, id
dialog option name or form option label	optionName, name, optionText, text, optionTitle, title, optionLabel, label
field id	fieldId, id
field type	fieldType, type
field required	fieldRequired, required
field label	fieldLabel, label
field hint	fieldHint, hint
field value	fieldValue, value
field minimum length	fieldMinimumLength, minimumLength
field maximum length	fieldMaximumLength, maximumLength
field regex	fieldRegex, regex
field prefix	fieldPrefix, prefix
field suffix	fieldSuffix, suffix
field decimals	fieldDecimals, decimals
field minimum value	fieldMinimumValue, minimumValue, minValue
field maximum value	fieldMaximumValue, maximumValue, maxValue
field allow negative	fieldAllowNegative, allowNegative, negative
field future only	fieldFutureOnly, futureOnly
field past only	fieldPastOnly, pastOnly
field earliest date	fieldEarliestDate, earliestDate
field latest date	fieldLatestDate, latestDate
field sunday	sunday, sun, zondag, zo
field monday	monday, mon, maandag, ma
field tuesday	tuesday, tue, dinsdag, di
field wednesday	wednesday, wed, woensdag, wo
field thursday	thursday, thu, donderdag, do
field friday	friday, fri, vrijdag, vr
field saturday	saturday, sat, zaterdag, za
field multiple	fieldMultiple, multiple
field columns	fieldColumns, columns
field options	fieldOptions, options
option selected	optionSelected, selected
option article number	optionArticleNumber, articleNumber
option barcode	optionBarcode, barcode
option plu number	optionPluNumber, pluNumber, plu
option supplier article number	optionSupplierArticleNumber, supplierArticleNumber
option ext article id	optionExtArticleId, extArticleId
form field or form option color	fieldColor, fieldColour, color, colour
dialog option color	optionColor, optionColour, color, colour
request id	requestId, id
request title	requestTitle, title
custom action id	customActionId, id
button caption	buttonCaption, caption
card identifier	cardIdentifier, identifier, id
card balance	cardBalance, balance
card description	cardDescription, description, desc
card expiration	cardExpiration, expiration
card blocked	cardBlocked, blocked
new balance	isNewBalance, isNewCardBalance, newBalance, newCardBalance, isNew, new
hide timestamp	hideTimestamp, noTimestamp
monospaced font	monospaced, monospacedFont
clear screen	clear, clearScreen, clearMessage, clearMessages
clear customer screen	clearCustomer, clearCustomerMessage, clearCustomerMessages, clearCustomerScreen
message	message, text, textBefore
message after	messageAfter, textAfter
customer message	customerMessage, customerText
display time	displayTime, time
background color	backgroundColor, backgroundColour
barcode	barcode, qrcode, code
print separate	printSeparate, separate
external version	version, externalVersion
auto open	autoOpen, auto
url title	urlTitle, title
minimum width	minimumWidth, minWidth
minimum height	minimumHeight, minHeight

The exact root aliases displayQrcode and hideQrcode are accepted for displayBarcode and hideBarcode. enabled is the inverse of disabled in dialog and form options. error.message also accepts text. annotations and entity have no alternate spelling at the annotation-item level; entity identifier properties have the first-character normalization described above.

Error code reference

The following codes are defined in this checkout. Some identify local transport or validation failures and are not necessarily delivered as an error webhook. Inspect error.message for the specific cause. Consumer-returned error.code is a string and is not restricted to this list.

Code	Meaning
INVALID_SIGNATURE	The supplied request signature is invalid.
NO_SIGNATURE	Required signature is absent.
INVALID_JSON	The response body cannot be parsed as JSON.
INVALID_DATA	A response value has an invalid type or value.
INVALID_SUBSCRIPTION_ID	The subscription identifier is invalid.
NO_SUBSCRIPTION_ID	Required subscription identifier is absent.
NO_CONTENT_TYPE	Required content type is absent.
INVALID_CONTENT_TYPE	The content type is unsupported.
NO_EVENT_DETAILS	Required event metadata is absent.
NO_SCANNED_CODE	Required scanned code is absent.
LINE_ALREADY_HAS_DISCOUNT	A conflicting existing discount prevents the requested change.
LINE_ALREADY_HAS_DISCOUNT_FROM_OTHER_WEBHOOK	The existing discount belongs to a different webhook consumer.
INVALID_LINE_ID	The line reference is invalid for the session.
LINE_ID_ALREADY_EXISTS	The proposed line identifier is already in use.
INVALID_RELATION_NUMBER	The relation reference is invalid.
INVALID_ARTICLE	The supplied article references cannot be resolved.
INVALID_DISCOUNT_PERCENTAGE	The discount percentage is outside the permitted range.
INVALID_RECEIPT_FOOTER_TEXT	The receipt footer text fails validation.
INVALID_RECEIPT_FOOTER_CODE	The barcode contents fail validation.
INVALID_RECEIPT_FOOTER_CODE_TYPE	The receipt barcode type is unsupported.
LINE_CHANGE_NOT_ALLOWED	The event, document or consumer permissions prohibit this line change.
LINE_ADDITION_NOT_ALLOWED	The event or document does not allow line additions.
LINE_DELETION_NOT_ALLOWED	The event, document or consumer permissions prohibit this deletion.
INVALID_EXTERNAL_PAYMENT_ID	The external payment identifier is invalid or does not match the active payment.
EXTERNAL_PAYMENT_ID_ALREADY_USED	The external payment identifier has already been used.
MISSING_REQUIRED_BODY	This event requires a nonempty response body.
MISSING_REQUIRED_FIELD	A required response property is missing or unusable.
FINAL_AMOUNT_ADJUSTMENT_NOT_ALLOWED	Changing the external payment amount is disabled.
LOWER_FINAL_AMOUNT_NOT_ALLOWED	A lower final amount is not allowed in this payment flow.
HIGHER_FINAL_AMOUNT_NOT_ALLOWED	A higher final amount is not allowed in this payment flow.
HTTP_PARSING_ERROR	The HTTP response could not be parsed.
WEBHOOK_CANCELLED_BY_USER	The user cancelled the webhook interaction.
RESPONSE_NOT_ALLOWED_HERE	This response action is not allowed for the current event or context.
UNEXPECTED_FIELD	An unexpected response field was reported. General root-field rejection is disabled in this checkout.
WEBHOOK_TIMED_OUT	The webhook request timed out.
INVALID_PAYMENT_METHOD	The requested payment method is not permitted for this consumer.
ACTIVE_SESSION_CHANGED	The active session changed during webhook handling.
JWT_AUTHENTICATION	Authentication-token acquisition failed.
INVALID_APPLY_TO_QUANTITY	Discount quantity has the wrong sign or exceeds the available quantity.
PREPAY_TABLE_FAILED	The table prepayment could not be registered.

Timeouts and JWT authentication failures are not sent back as error webhooks. User cancellation during start/poll external payment is handled through the cancellation flow instead of a redundant error callback.