Payments

GET /v1/customers/{customerId}/credit-balance

Customer credit balance

payments:read

What the customer has to their credit — from credit notes on paid invoices, or from OVERPAYMENTS. Append-only ledger; the balance is the sum.

Parameter	In	Type	Required	Description
customerId	path	string	Yes

Request exampleNo request body

curl

curl https://api.rieckflow.com/v1/customers/9b2f1c1e-…/credit-balance \
  -H "Authorization: Bearer $RIECK_API_KEY"

TypeScript

const svar = await rieck.request("GET", "/v1/customers/9b2f1c1e-…/credit-balance");

Response

{
  "data": {
    "customerId": "467a0d8d-b9b2-4df3-bf7b-17d649442890",
    "balanceOere": 31250,
    "movements": [
      {
        "id": "9b2f1c1e-6b87-4d9b-91a0-47c8d72b8440",
        "type": "arose",
        "amountOere": 31250,
        "creditNoteId": null,
        "creditNoteNumber": null,
        "invoiceId": "5c0d10ec-f086-48c6-b1c7-b389a47ac6d1",
        "invoiceNumber": 1042,
        "reason": "overpayment",
        "createdAt": "2026-08-08T12:05:44Z"
      }
    ]
  }
}

200 Never negative. movements[].type is arose | offset | refund_declared.application/json

Response fields 2

Field	Type	Description
data.balanceOere	integer	Customer credit available for refund or offset.
data.movements	object[]	Append-only credit ledger, newest first.

Possible errors 5

HTTP	Code	Meaning
401	invalid_api_key	The API key is missing, invalid, expired or revoked.
403	api_not_included	The organisation’s plan does not include API access.
403	insufficient_scope	The key does not have the required scope.
404	customer_not_found	The customer does not exist or belongs to another organisation.
429	rate_limited	The organisation’s rate budget is exhausted.

---

POST /v1/customers/{customerId}/refunds

Declare a refund

payments:write

Records that YOU state the credit was paid back — a declaration, not a transfer: we never see your bank account, and this endpoint moves no money. Rejected with funds_not_settled_yet while the money is still in our client funds (you cannot have forwarded what you have not received) — offset it against the next invoice instead, which happens automatically on issue. Append-only: it cannot be silently undone.

Parameter	In	Type	Required	Description
customerId	path	string	Yes

Request body fields 2

Field	Type	Required	Description
amountOere	integer	Yes	Amount in integer øre. 125000 means DKK 1,250.00.
reason	string	No	Field in the request payload.

Request exampleapplication/json

curl

curl -X POST https://api.rieckflow.com/v1/customers/9b2f1c1e-…/refunds \
  -H "Authorization: Bearer $RIECK_API_KEY" \
  -H "Idempotency-Key: order-2041" \
  -H "Content-Type: application/json" \
  -d '{
    "amountOere": 125000,
    "reason": "Ordered by mistake"
  }'

TypeScript

const svar = await rieck.request("POST", "/v1/customers/9b2f1c1e-…/refunds", {
  body: {
    "amountOere": 125000,
    "reason": "Ordered by mistake"
  },
});

Response

{
  "data": {
    "creditBalanceOere": 0,
    "declared": true
  }
}

200 Success envelopeapplication/json

Possible errors 10

HTTP	Code	Meaning
400	invalid_idempotency_key	Idempotency-Key is missing or malformed.
400	invalid_request	The request body or parameter failed validation.
401	invalid_api_key	The API key is missing, invalid, expired or revoked.
403	api_not_included	The organisation’s plan does not include API access.
403	insufficient_scope	The key does not have the required scope.
404	customer_not_found	The customer does not exist or belongs to another organisation.
409	idempotency_conflict	The same key was used with a different request.
409	idempotency_in_progress	The same operation is currently being processed. Retry later.
413	payload_too_large	The JSON or uploaded file exceeds this endpoint’s size limit.
429	rate_limited	The organisation’s rate budget is exhausted.

Request body — fuldt JSON Schema

{
  "type": "object",
  "properties": {
    "amountOere": {
      "type": "integer",
      "exclusiveMinimum": 0,
      "maximum": 9007199254740991
    },
    "reason": {
      "anyOf": [
        {
          "type": "string",
          "maxLength": 500
        },
        {
          "type": "null"
        }
      ]
    }
  },
  "required": [
    "amountOere"
  ],
  "additionalProperties": false
}

---

GET /v1/invoices/{invoiceId}/payments

List invoice payments

payments:read

Parameter	In	Type	Required	Description
invoiceId	path	string	Yes

Request exampleNo request body

curl

curl https://api.rieckflow.com/v1/invoices/9b2f1c1e-…/payments \
  -H "Authorization: Bearer $RIECK_API_KEY"

TypeScript

const svar = await rieck.request("GET", "/v1/invoices/9b2f1c1e-…/payments");

Response

{
  "data": [
    {
      "id": "9b2f1c1e-6b87-4d9b-91a0-47c8d72b8440",
      "invoiceId": "5c0d10ec-f086-48c6-b1c7-b389a47ac6d1",
      "amountOere": 156250,
      "paymentDate": "2026-08-08",
      "source": "bank_transfer",
      "pspFeeOere": 0,
      "hasReceipt": true,
      "createdAt": "2026-08-08T12:05:44Z"
    }
  ]
}

200 Success envelopeapplication/json

Response fields 6

Field	Type	Description
data.id	uuid	Stable payment id.
data.invoiceId	uuid	Invoice the payment belongs to.
data.amountOere	integer	Payment amount in øre.
data.paymentDate	date	Bank value date.
data.source	string	How the payment was registered.
data.hasReceipt	boolean	Whether a receipt can be downloaded.

Possible errors 5

HTTP	Code	Meaning
401	invalid_api_key	The API key is missing, invalid, expired or revoked.
403	api_not_included	The organisation’s plan does not include API access.
403	insufficient_scope	The key does not have the required scope.
404	invoice_not_found	The invoice does not exist or belongs to another organisation.
429	rate_limited	The organisation’s rate budget is exhausted.

---

POST /v1/invoices/{invoiceId}/payments

Register manual payment

payments:write

Your Idempotency-Key IS the bookkeeping key — the same key never registers twice.

Parameter	In	Type	Required	Description
invoiceId	path	string	Yes

Request body fields 2

Field	Type	Required	Description
amountOere	integer	Yes	Amount in integer øre. 125000 means DKK 1,250.00.
paymentDate	string	Yes	Field in the request payload.

Request exampleapplication/json

curl

curl -X POST https://api.rieckflow.com/v1/invoices/9b2f1c1e-…/payments \
  -H "Authorization: Bearer $RIECK_API_KEY" \
  -H "Idempotency-Key: order-2041" \
  -H "Content-Type: application/json" \
  -d '{
    "amountOere": 125000,
    "paymentDate": "2026-08-15"
  }'

TypeScript

const svar = await rieck.request("POST", "/v1/invoices/9b2f1c1e-…/payments", {
  body: {
    "amountOere": 125000,
    "paymentDate": "2026-08-15"
  },
});

Response

{
  "data": {
    "id": "9b2f1c1e-6b87-4d9b-91a0-47c8d72b8440",
    "invoiceNumber": 1042,
    "type": "invoice",
    "status": "issued",
    "customerId": "467a0d8d-b9b2-4df3-bf7b-17d649442890",
    "issuedDate": "2026-08-04",
    "dueDate": "2026-08-18",
    "netOere": 125000,
    "vatOere": 31250,
    "grossOere": 156250,
    "paidOere": 0,
    "creditedOere": 0,
    "reminderFeeOere": 0,
    "balanceOere": 156250,
    "reminderCount": 0,
    "collectionsCaseId": null,
    "externalReference": "order-2041",
    "metadata": null,
    "createdAt": "2026-08-04T09:32:11Z"
  },
  "meta": {
    "outcome": "paid",
    "paymentId": "9b2f1c1e-6b87-4d9b-91a0-47c8d72b8440"
  }
}

201 Success envelopeapplication/json

Response fields 8

Field	Type	Description
data.id	uuid	Stable invoice id.
data.invoiceNumber	integer | null	Sequential number. Null while the invoice is a draft.
data.status	draft | issued | paid | overdue | collections	Stored lifecycle status.
data.grossOere	integer	Invoice total including VAT.
data.paidOere	integer	Total registered payments.
data.balanceOere	integer	Amount still owed now.
data.collectionsCaseId	uuid | null	Collection case created from this invoice.
data.externalReference	string | null	Your reconciliation reference.

Possible errors 10

HTTP	Code	Meaning
400	invalid_idempotency_key	Idempotency-Key is missing or malformed.
400	invalid_request	The request body or parameter failed validation.
401	invalid_api_key	The API key is missing, invalid, expired or revoked.
403	api_not_included	The organisation’s plan does not include API access.
403	insufficient_scope	The key does not have the required scope.
404	invoice_not_found	The invoice does not exist or belongs to another organisation.
409	idempotency_conflict	The same key was used with a different request.
409	idempotency_in_progress	The same operation is currently being processed. Retry later.
413	payload_too_large	The JSON or uploaded file exceeds this endpoint’s size limit.
429	rate_limited	The organisation’s rate budget is exhausted.

Request body — fuldt JSON Schema

{
  "type": "object",
  "properties": {
    "amountOere": {
      "type": "integer",
      "minimum": 1,
      "maximum": 100000000000
    },
    "paymentDate": {
      "type": "string",
      "pattern": "^\\d{4}-\\d{2}-\\d{2}$"
    }
  },
  "required": [
    "amountOere",
    "paymentDate"
  ],
  "additionalProperties": false
}

---

GET /v1/invoices/{invoiceId}/payment-link

Get payment link

payments:read

Parameter	In	Type	Required	Description
invoiceId	path	string	Yes

Request exampleNo request body

curl

curl https://api.rieckflow.com/v1/invoices/9b2f1c1e-…/payment-link \
  -H "Authorization: Bearer $RIECK_API_KEY"

TypeScript

const svar = await rieck.request("GET", "/v1/invoices/9b2f1c1e-…/payment-link");

Response

{
  "data": {
    "url": "https://pay.rieckflow.com/p/RIE-7K3M2-Q9F4P",
    "reference": "order-2041",
    "paymentCode": "RIE-7K3M2-Q9F4P",
    "balanceOere": 156250
  }
}

200 Success envelopeapplication/json

Response fields 4

Field	Type	Description
data.url	url	Hosted payment page for this invoice.
data.reference	string	Reference used for reconciliation.
data.paymentCode	string	Short code the customer can type on the payment site.
data.balanceOere	integer	Current amount due when the link is requested.

Possible errors 5

HTTP	Code	Meaning
401	invalid_api_key	The API key is missing, invalid, expired or revoked.
403	api_not_included	The organisation’s plan does not include API access.
403	insufficient_scope	The key does not have the required scope.
404	invoice_not_found	The invoice does not exist or belongs to another organisation.
429	rate_limited	The organisation’s rate budget is exhausted.

---

POST /v1/invoices/{invoiceId}/payment-link

Mint payment link (idempotent)

payments:write

Parameter	In	Type	Required	Description
invoiceId	path	string	Yes

Request exampleNo request body

curl

curl -X POST https://api.rieckflow.com/v1/invoices/9b2f1c1e-…/payment-link \
  -H "Authorization: Bearer $RIECK_API_KEY" \
  -H "Idempotency-Key: order-2041"

TypeScript

const svar = await rieck.request("POST", "/v1/invoices/9b2f1c1e-…/payment-link");

Response

{
  "data": {
    "url": "https://pay.rieckflow.com/p/RIE-7K3M2-Q9F4P",
    "reference": "order-2041",
    "paymentCode": "RIE-7K3M2-Q9F4P",
    "balanceOere": 156250
  }
}

200 Success envelopeapplication/json

Response fields 4

Field	Type	Description
data.url	url	Hosted payment page for this invoice.
data.reference	string	Reference used for reconciliation.
data.paymentCode	string	Short code the customer can type on the payment site.
data.balanceOere	integer	Current amount due when the link is requested.

Possible errors 8

HTTP	Code	Meaning
400	invalid_idempotency_key	Idempotency-Key is missing or malformed.
401	invalid_api_key	The API key is missing, invalid, expired or revoked.
403	api_not_included	The organisation’s plan does not include API access.
403	insufficient_scope	The key does not have the required scope.
404	invoice_not_found	The invoice does not exist or belongs to another organisation.
409	idempotency_conflict	The same key was used with a different request.
409	idempotency_in_progress	The same operation is currently being processed. Retry later.
429	rate_limited	The organisation’s rate budget is exhausted.

---

POST /v1/checkout-sessions

Mint a checkout session for your own UI

payments:write

Your SERVER calls this with your secret key; your BROWSER only ever loads embedUrl. The reference is an unguessable capability that can pay exactly this one invoice — the client_secret model, with no publishable key to leak. Idempotent: the reference is minted once per invoice and reused. balanceOere is indicative only, because the gateway session is minted when the payer clicks, always on the CURRENT outstanding amount.

Request body fields 1

Field	Type	Required	Description
invoiceId	string	Yes	Field in the request payload.

Request exampleapplication/json

curl

curl -X POST https://api.rieckflow.com/v1/checkout-sessions \
  -H "Authorization: Bearer $RIECK_API_KEY" \
  -H "Idempotency-Key: order-2041" \
  -H "Content-Type: application/json" \
  -d '{
    "invoiceId": "9b2f1c1e-…"
  }'

TypeScript

const svar = await rieck.request("POST", "/v1/checkout-sessions", {
  body: {
    "invoiceId": "9b2f1c1e-…"
  },
});

Response

{
  "data": {
    "id": "9b2f1c1e-6b87-4d9b-91a0-47c8d72b8440",
    "invoiceId": "5c0d10ec-f086-48c6-b1c7-b389a47ac6d1",
    "amountOere": 156250,
    "paymentDate": "2026-08-08",
    "source": "bank_transfer",
    "pspFeeOere": 0,
    "hasReceipt": true,
    "createdAt": "2026-08-08T12:05:44Z"
  }
}

201 Success envelopeapplication/json

Response fields 6

Field	Type	Description
data.id	uuid	Stable payment id.
data.invoiceId	uuid	Invoice the payment belongs to.
data.amountOere	integer	Payment amount in øre.
data.paymentDate	date	Bank value date.
data.source	string	How the payment was registered.
data.hasReceipt	boolean	Whether a receipt can be downloaded.

Possible errors 9

HTTP	Code	Meaning
400	invalid_idempotency_key	Idempotency-Key is missing or malformed.
400	invalid_request	The request body or parameter failed validation.
401	invalid_api_key	The API key is missing, invalid, expired or revoked.
403	api_not_included	The organisation’s plan does not include API access.
403	insufficient_scope	The key does not have the required scope.
409	idempotency_conflict	The same key was used with a different request.
409	idempotency_in_progress	The same operation is currently being processed. Retry later.
413	payload_too_large	The JSON or uploaded file exceeds this endpoint’s size limit.
429	rate_limited	The organisation’s rate budget is exhausted.

Request body — fuldt JSON Schema

{
  "type": "object",
  "properties": {
    "invoiceId": {
      "type": "string",
      "format": "uuid",
      "pattern": "^([0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[1-8][0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}|00000000-0000-0000-0000-000000000000|ffffffff-ffff-ffff-ffff-ffffffffffff)$"
    }
  },
  "required": [
    "invoiceId"
  ],
  "additionalProperties": false
}

---

GET /v1/payments

List payments (org-wide)

payments:read

Parameter	In	Type	Required	Description
limit	query	integer	No	Page size, 1-200 (default 50)
cursor	query	string	No	Opaque cursor from meta.nextCursor

Request exampleNo request body

curl

curl https://api.rieckflow.com/v1/payments \
  -H "Authorization: Bearer $RIECK_API_KEY"

TypeScript

const svar = await rieck.request("GET", "/v1/payments");

Response

{
  "data": [
    {
      "id": "9b2f1c1e-6b87-4d9b-91a0-47c8d72b8440",
      "invoiceId": "5c0d10ec-f086-48c6-b1c7-b389a47ac6d1",
      "amountOere": 156250,
      "paymentDate": "2026-08-08",
      "source": "bank_transfer",
      "pspFeeOere": 0,
      "hasReceipt": true,
      "createdAt": "2026-08-08T12:05:44Z"
    }
  ],
  "meta": {
    "nextCursor": null
  }
}

200 Success envelopeapplication/json

Response fields 7

Field	Type	Description
data[].id	uuid	Stable payment id.
data[].invoiceId	uuid	Invoice the payment belongs to.
data[].amountOere	integer	Payment amount in øre.
data[].paymentDate	date	Bank value date.
data[].source	string	How the payment was registered.
data[].hasReceipt	boolean	Whether a receipt can be downloaded.
meta.nextCursor	`string	null`

Possible errors 5

HTTP	Code	Meaning
400	invalid_cursor	The cursor is malformed, expired or belongs to another list shape.
401	invalid_api_key	The API key is missing, invalid, expired or revoked.
403	api_not_included	The organisation’s plan does not include API access.
403	insufficient_scope	The key does not have the required scope.
429	rate_limited	The organisation’s rate budget is exhausted.

---

GET /v1/payments/{paymentId}/receipt

Receipt PDF

payments:read

Parameter	In	Type	Required	Description
paymentId	path	string	Yes

Request exampleNo request body

curl

curl https://api.rieckflow.com/v1/payments/9b2f1c1e-…/receipt \
  -H "Authorization: Bearer $RIECK_API_KEY"

TypeScript

const svar = await rieck.request("GET", "/v1/payments/9b2f1c1e-…/receipt");

200 Success envelopeapplication/pdf

Possible errors 4

HTTP	Code	Meaning
401	invalid_api_key	The API key is missing, invalid, expired or revoked.
403	api_not_included	The organisation’s plan does not include API access.
403	insufficient_scope	The key does not have the required scope.
429	rate_limited	The organisation’s rate budget is exhausted.

---

DELETE /v1/payments/{paymentId}

Undo a manually registered payment

payments:write

Manual registrations only, and only while the invoice is still the creditor’s own: 422 once it has been handed to collections, settled to the creditor, or its overpayment credit has been used. The registration’s Idempotency-Key is spent afterwards — re-register with a new one.

Parameter	In	Type	Required	Description
paymentId	path	string	Yes

Request exampleNo request body

curl

curl -X DELETE https://api.rieckflow.com/v1/payments/9b2f1c1e-… \
  -H "Authorization: Bearer $RIECK_API_KEY" \
  -H "Idempotency-Key: order-2041"

TypeScript

const svar = await rieck.request("DELETE", "/v1/payments/9b2f1c1e-…");

Response

{
  "data": {
    "id": "9b2f1c1e-6b87-4d9b-91a0-47c8d72b8440",
    "invoiceId": "5c0d10ec-f086-48c6-b1c7-b389a47ac6d1",
    "amountOere": 156250,
    "paymentDate": "2026-08-08",
    "source": "bank_transfer",
    "pspFeeOere": 0,
    "hasReceipt": true,
    "createdAt": "2026-08-08T12:05:44Z"
  }
}

200 Success envelopeapplication/json

Response fields 6

Field	Type	Description
data.id	uuid	Stable payment id.
data.invoiceId	uuid	Invoice the payment belongs to.
data.amountOere	integer	Payment amount in øre.
data.paymentDate	date	Bank value date.
data.source	string	How the payment was registered.
data.hasReceipt	boolean	Whether a receipt can be downloaded.

Possible errors 7

HTTP	Code	Meaning
400	invalid_idempotency_key	Idempotency-Key is missing or malformed.
401	invalid_api_key	The API key is missing, invalid, expired or revoked.
403	api_not_included	The organisation’s plan does not include API access.
403	insufficient_scope	The key does not have the required scope.
409	idempotency_conflict	The same key was used with a different request.
409	idempotency_in_progress	The same operation is currently being processed. Retry later.
429	rate_limited	The organisation’s rate budget is exhausted.