# POST /api/invoicing/credit-notes/{id}/issue

Credit Notes: Issues a draft credit note and applies it to the invoice it credits.

The credit note is given the next number from the biller's credit note sequence (for example
`CN-2026-00001`), separate from its invoice numbers, and its issue date is set. From then on
it can no longer be edited or deleted. Its total is applied to the original invoice at once: the
invoice's `amountCredited` rises by the total, its `balanceDue` falls by it, and a
credit that leaves nothing owed moves the invoice to `Paid`, invalidates its payment link
and publishes the `Invoice.Paid` webhook. A credit that leaves a balance owed moves the
payment link onto the new balance and leaves the invoice status as it was. The invoice
recipient is emailed the credit note; a failed email does not undo the credit.

The call is safe to repeat. A credit note that is already applied is returned unchanged, and the
same credit is never applied to an invoice twice.

**Operation ID:** `creditNoteIssueAndApply`

## Authorization

Requires: Invoicing.CreditNotes, Invoicing.CreditNotes.Issue, merchant scope.

Requires API key scope: `admin`

Required permissions:
- `Invoicing.CreditNotes`
- `Invoicing.CreditNotes.Issue`

## Parameters

| Name | In | Required | Type | Description |
| --- | --- | --- | --- | --- |
| id | path | yes | string(uuid) | The credit note id. |
| suppressNulls | query | no | boolean | If true, omit properties with null values. |

## Responses

### 200

The credit note, now `Applied`, with its number and dates.

**Content type:** `application/json`

Schema: [`CreditNoteDto`](https://devportal.signapay-sbx.winkpg.io/docs/api/models/CreditNoteDto.md)

Properties:
- `id` (string(uuid))
- `creationTime` (string(date-time)): The date and time when this entity was created.
- `creatorId` (string(uuid)): The ID of the user who created this entity. (nullable)
- `lastModificationTime` (string(date-time)): The date and time when this entity was last modified. (nullable)
- `lastModifierId` (string(uuid)): The ID of the user who last modified this entity. (nullable)
- `billerId` (string(uuid))
- `billerType` ([InvoicePartyType](https://devportal.signapay-sbx.winkpg.io/docs/api/models/InvoicePartyType.md)): Identifies the type of entity acting as the biller or recipient on an invoice.
  Values:
  - `GatewayOwner`: Platform-level gateway owner.
  - `Reseller`: Reseller entity.
  - `Merchant`: Merchant entity.
  - `Customer`: End customer.
- `creditNoteNumber` (string): (nullable)
- `originalInvoiceId` (string(uuid))
- `customerId` (string(uuid)): (nullable)
- `reason` (string): (nullable)
- `lineItems` (array<[CreditNoteLineItemDto](https://devportal.signapay-sbx.winkpg.io/docs/api/models/CreditNoteLineItemDto.md)>): (nullable)
  Fields of each item:
  - `id` (string(uuid))
  - `originalLineItemId` (string(uuid)): (nullable)
  - `description` (string): (nullable)
  - `quantity` (number(double))
  - `unitPrice` (number(double))
  - `taxAmount` (number(double)): Tax credited on this line, as computed server-side.
  - `lineTotal` (number(double)): Net plus tax credited on this line, as computed server-side.
- `total` (number(double)): (nullable)
- `status` ([CreditNoteStatus](https://devportal.signapay-sbx.winkpg.io/docs/api/models/CreditNoteStatus.md)): Lifecycle status of a credit note.
  Values:
  - `Draft`: Created, not yet issued.
  - `Issued`: Issued and available to apply.
  - `Applied`: Applied to the original invoice.
  - `Voided`: Voided and no longer valid.
- `issuedAt` (string(date-time)): (nullable)
- `appliedAt` (string(date-time)): (nullable)
- `concurrencyStamp` (string): (nullable)

### 429

The request was refused because a rate limit was exceeded, or because something a later retry can clear stopped it. A rate limit refusal carries an `application/problem+json` body: wait at least the interval `Retry-After` names before retrying, then back off. Limits are tuned per deployment, so read the allowance from the response headers rather than assuming a fixed ceiling. Any other refusal carries the standard error envelope as `application/json`, and its `error.code` names the cause.

**Content type:** `application/problem+json`

Schema: [`RateLimitProblemDetails`](https://devportal.signapay-sbx.winkpg.io/docs/api/models/RateLimitProblemDetails.md)

Properties:
- `type` (string) required: The problem type identifier. Always the same value: the failure is the status code itself, so there is no sub-type for a caller to branch on. (nullable)
- `title` (string) required: A short, human-readable summary of the problem type. (nullable)
- `status` (integer(int32)) required: The HTTP status code, repeated in the body as the problem-details format defines.
- `detail` (string) required: A human-readable explanation of this occurrence of the problem. (nullable)
- `retryAfterSeconds` (integer(int32)) required: How long to wait before retrying, in whole seconds, carrying the same figure as the `Retry-After` header. Always at least one: a value of zero would invite an immediate retry that is certain to be rejected again.

**Content type:** `application/json`

Schema: [`RemoteServiceErrorResponse`](https://devportal.signapay-sbx.winkpg.io/docs/api/models/RemoteServiceErrorResponse.md)

Properties:
- `error` ([RemoteServiceErrorInfo](https://devportal.signapay-sbx.winkpg.io/docs/api/models/RemoteServiceErrorInfo.md))

### 400

Bad request. The request was malformed or failed validation. When validation rejected it, `error.validationErrors` names each member at fault and why.

**Content type:** `application/json`

Schema: [`RemoteServiceErrorResponse`](https://devportal.signapay-sbx.winkpg.io/docs/api/models/RemoteServiceErrorResponse.md)

Properties:
- `error` ([RemoteServiceErrorInfo](https://devportal.signapay-sbx.winkpg.io/docs/api/models/RemoteServiceErrorInfo.md))

_Example: Request failed validation_

One or more fields were rejected before any rule ran. error.code is null on the envelope and the causes are in validationErrors, one entry per failure. An entry carries code when the validator declared a publishable one, and memberPaths when the full path says more than members does (an element inside a collection, for example). Both keys are omitted when they would add nothing.

```json
{
  "error": {
    "code": null,
    "message": "Your request is not valid!",
    "details": "The following errors were detected during validation.",
    "data": {
      "correlationId": "0123456789abcdef0123456789abcdef"
    },
    "validationErrors": [
      {
        "message": "'Amount' must be greater than 0.",
        "members": [
          "amount"
        ]
      },
      {
        "message": "The card has expired.",
        "members": [
          "expirationDate"
        ],
        "code": "CardData:CardExpired"
      },
      {
        "message": "'Value' must not be empty.",
        "members": [
          "value"
        ],
        "memberPaths": [
          "customFields[2].value"
        ]
      }
    ]
  }
}
```

### 401

Unauthorized. The request carried no API key or signed-in session, or the key it carried is invalid, revoked or expired.

**Content type:** `application/json`

Schema: [`RemoteServiceErrorResponse`](https://devportal.signapay-sbx.winkpg.io/docs/api/models/RemoteServiceErrorResponse.md)

Properties:
- `error` ([RemoteServiceErrorInfo](https://devportal.signapay-sbx.winkpg.io/docs/api/models/RemoteServiceErrorInfo.md))

### 403

Forbidden. The API key lacks the scope this operation needs, the signed-in user lacks the permission, or a business rule refused the request. The error code in the body names the reason.

**Content type:** `application/json`

Schema: [`RemoteServiceErrorResponse`](https://devportal.signapay-sbx.winkpg.io/docs/api/models/RemoteServiceErrorResponse.md)

Properties:
- `error` ([RemoteServiceErrorInfo](https://devportal.signapay-sbx.winkpg.io/docs/api/models/RemoteServiceErrorInfo.md))

### 404

No credit note has this id for the caller (`Invoicing:CreditNote:NotFound`).

**Content type:** `application/json`

Schema: [`RemoteServiceErrorResponse`](https://devportal.signapay-sbx.winkpg.io/docs/api/models/RemoteServiceErrorResponse.md)

Properties:
- `error` ([RemoteServiceErrorInfo](https://devportal.signapay-sbx.winkpg.io/docs/api/models/RemoteServiceErrorInfo.md))

_Example: Resource not found_

The id in the path names no record the caller can see. Most resources answer with a null error.code and a message naming the resource type and the id; a resource that publishes a not-found code in the catalog above carries it in error.code instead, so check for one before matching on the message.

```json
{
  "error": {
    "code": null,
    "message": "There is no entity Transaction with id = 7d1f3a52-0c4e-4b8a-9e21-5a6b7c8d9e00!",
    "details": null,
    "data": {
      "correlationId": "0123456789abcdef0123456789abcdef"
    },
    "validationErrors": null
  }
}
```

### 409

The credit cannot be applied, and nothing changed: the invoice is not `Sent`, `Viewed`,
`PartiallyPaid` or `PastDue` (`Invoicing:CreditNote:InvalidInvoiceStatus`), the
credit note total is zero (`Invoicing:CreditNote:TotalNotPositive`), the total is above the
invoice's balance due (`Invoicing:CreditNote:ExceedsBalance`; money already paid is returned
with a refund instead), or the credit note is in a status that cannot be issued
(`Invoicing:CreditNote:InvalidStatus`).

**Content type:** `application/json`

Schema: [`RemoteServiceErrorResponse`](https://devportal.signapay-sbx.winkpg.io/docs/api/models/RemoteServiceErrorResponse.md)

Properties:
- `error` ([RemoteServiceErrorInfo](https://devportal.signapay-sbx.winkpg.io/docs/api/models/RemoteServiceErrorInfo.md))

### 500

Internal server error. The platform failed unexpectedly while handling the request. If it keeps failing, contact support and quote the correlation id, which the response carries in the `X-Correlation-Id` header and as `error.data.correlationId`.

**Content type:** `application/json`

Schema: [`RemoteServiceErrorResponse`](https://devportal.signapay-sbx.winkpg.io/docs/api/models/RemoteServiceErrorResponse.md)

Properties:
- `error` ([RemoteServiceErrorInfo](https://devportal.signapay-sbx.winkpg.io/docs/api/models/RemoteServiceErrorInfo.md))

### 501

Not implemented. The operation is declared but has no implementation on this deployment, so no request to it can succeed. Retrying does not help.

**Content type:** `application/json`

Schema: [`RemoteServiceErrorResponse`](https://devportal.signapay-sbx.winkpg.io/docs/api/models/RemoteServiceErrorResponse.md)

Properties:
- `error` ([RemoteServiceErrorInfo](https://devportal.signapay-sbx.winkpg.io/docs/api/models/RemoteServiceErrorInfo.md))

### default

The request failed. The body carries the standard error envelope: a machine-readable `error.code`, a human-readable `error.message`, and `error.validationErrors` when the failure was a validation rejection. The [error reference](https://devportal.signapay-sbx.winkpg.io/docs/errors.md) lists the values `error.code` can take.

**Content type:** `application/json`

Schema: [`RemoteServiceErrorResponse`](https://devportal.signapay-sbx.winkpg.io/docs/api/models/RemoteServiceErrorResponse.md)

Properties:
- `error` ([RemoteServiceErrorInfo](https://devportal.signapay-sbx.winkpg.io/docs/api/models/RemoteServiceErrorInfo.md))

_Example: Business rule refused the request_

The request was understood and rejected by a platform rule. This is the shape that carries a code from the catalog above, so branch on error.code rather than on the message text. The HTTP status is the one listed against the code.

```json
{
  "error": {
    "code": "Transactions:OperationNotAllowed",
    "message": "The operation 'Void' is not allowed on a Sale transaction with result 'Approved' and settlement state 'Settled'.",
    "details": null,
    "data": {
      "correlationId": "0123456789abcdef0123456789abcdef"
    },
    "validationErrors": null
  }
}
```

### Errors

These statuses answer with the error envelope outlined below.

- `400`: Bad request. The request was malformed or failed validation. When validation rejected it, `error.validationErrors` names each member at fault and why.
- `401`: Unauthorized. The request carried no API key or signed-in session, or the key it carried is invalid, revoked or expired.
- `403`: Forbidden. The API key lacks the scope this operation needs, the signed-in user lacks the permission, or a business rule refused the request. The error code in the body names the reason.
- `404`: No credit note has this id for the caller (`Invoicing:CreditNote:NotFound`).
- `409`: The credit cannot be applied, and nothing changed: the invoice is not `Sent`, `Viewed`, `PartiallyPaid` or `PastDue` (`Invoicing:CreditNote:InvalidInvoiceStatus`), the credit note total is zero (`Invoicing:CreditNote:TotalNotPositive`), the total is above the invoice's balance due (`Invoicing:CreditNote:ExceedsBalance`; money already paid is returned with a refund instead), or the credit note is in a status that cannot be issued (`Invoicing:CreditNote:InvalidStatus`).
- `500`: Internal server error. The platform failed unexpectedly while handling the request. If it keeps failing, contact support and quote the correlation id, which the response carries in the `X-Correlation-Id` header and as `error.data.correlationId`.
- `501`: Not implemented. The operation is declared but has no implementation on this deployment, so no request to it can succeed. Retrying does not help.
- `default`: The request failed. The body carries the standard error envelope: a machine-readable `error.code`, a human-readable `error.message`, and `error.validationErrors` when the failure was a validation rejection. The [error reference](https://devportal.signapay-sbx.winkpg.io/docs/errors.md) lists the values `error.code` can take.

**Content type:** `application/json`

Schema: [`RemoteServiceErrorResponse`](https://devportal.signapay-sbx.winkpg.io/docs/api/models/RemoteServiceErrorResponse.md)

Properties:
- `error` ([RemoteServiceErrorInfo](https://devportal.signapay-sbx.winkpg.io/docs/api/models/RemoteServiceErrorInfo.md))
  Fields:
  - `code` (string): (nullable)
  - `message` (string): (nullable)
  - `details` (string): (nullable)
  - `data` (object): (nullable)
  - `validationErrors` (array<[RemoteServiceValidationErrorInfo](https://devportal.signapay-sbx.winkpg.io/docs/api/models/RemoteServiceValidationErrorInfo.md)>): (nullable)

_Example: Request failed validation_

One or more fields were rejected before any rule ran. error.code is null on the envelope and the causes are in validationErrors, one entry per failure. An entry carries code when the validator declared a publishable one, and memberPaths when the full path says more than members does (an element inside a collection, for example). Both keys are omitted when they would add nothing.

```json
{
  "error": {
    "code": null,
    "message": "Your request is not valid!",
    "details": "The following errors were detected during validation.",
    "data": {
      "correlationId": "0123456789abcdef0123456789abcdef"
    },
    "validationErrors": [
      {
        "message": "'Amount' must be greater than 0.",
        "members": [
          "amount"
        ]
      },
      {
        "message": "The card has expired.",
        "members": [
          "expirationDate"
        ],
        "code": "CardData:CardExpired"
      },
      {
        "message": "'Value' must not be empty.",
        "members": [
          "value"
        ],
        "memberPaths": [
          "customFields[2].value"
        ]
      }
    ]
  }
}
```

## Authentication

- `ApiKey`

## Example request

Every block below sends the same request. Replace {{BASE_URL}} with the address of the API you are calling and {{API_KEY}} with your own key.

### cURL

```bash
curl -X POST "{{BASE_URL}}/api/invoicing/credit-notes/{id}/issue" \
  -H "api-key: {{API_KEY}}"
```

### PowerShell

```powershell
$headers = @{
    'api-key' = '{{API_KEY}}'
}

$response = Invoke-RestMethod -Method POST -Uri '{{BASE_URL}}/api/invoicing/credit-notes/{id}/issue' `
    -Headers $headers
```

### TypeScript (SDK)

```bash
npm install @winkpg/winkpg-api
```

```typescript
import { Configuration, InvoicingApi } from '@winkpg/winkpg-api';

const api = new InvoicingApi(new Configuration({
  basePath: '{{BASE_URL}}',
  apiKey: '{{API_KEY}}',
}));

const { data } = await api.creditNoteIssueAndApply("3fa85f64-5717-4562-b3fc-2c963f66afa6");
```

### TypeScript (raw HTTP)

```typescript
const response = await fetch('{{BASE_URL}}/api/invoicing/credit-notes/{id}/issue', {
  method: 'POST',
  headers: {
    "api-key": "{{API_KEY}}",
  },
});

const data = await response.json();
```

### C# (SDK)

```bash
dotnet add package WinkPg.Api.Client
```

```csharp
using WinkPg.Api.Client.Api;
using WinkPg.Api.Client.Client;

var config = new Configuration { BasePath = "{{BASE_URL}}" };
config.AddApiKey("api-key", "{{API_KEY}}");

var api = new InvoicingApi(config);
var result = await api.CreditNoteIssueAndApplyAsync(Guid.Parse("3fa85f64-5717-4562-b3fc-2c963f66afa6"));
```

### C# (raw HTTP)

```csharp
using var http = new HttpClient { BaseAddress = new Uri("{{BASE_URL}}") };

var request = new HttpRequestMessage(new HttpMethod("POST"), "/api/invoicing/credit-notes/{id}/issue");
request.Headers.Add("api-key", "{{API_KEY}}");

var response = await http.SendAsync(request);
response.EnsureSuccessStatusCode();
var json = await response.Content.ReadAsStringAsync();
```

### Python (SDK)

```bash
pip install winkpg-api
```

```python
import winkpg_api

configuration = winkpg_api.Configuration(host="{{BASE_URL}}")
configuration.api_key["ApiKey"] = "{{API_KEY}}"

with winkpg_api.ApiClient(configuration) as client:
    api = winkpg_api.InvoicingApi(client)
    result = api.credit_note_issue_and_apply("3fa85f64-5717-4562-b3fc-2c963f66afa6")
```

### Python (raw HTTP)

```bash
pip install requests
```

```python
import requests

headers = {
    "api-key": "{{API_KEY}}",
}

response = requests.request(
    "POST",
    "{{BASE_URL}}/api/invoicing/credit-notes/{id}/issue",
    headers=headers,
)
response.raise_for_status()
data = response.json()
```

## See also

- [All documentation](https://devportal.signapay-sbx.winkpg.io/llms.txt): the machine-readable index of every public page on this site.