# Update Credit Memo

`PATCH /accounting/credit-memos/{id}`

Group: Accounting › Credit Memos · Operation ID: `updateCreditMemo`

Updates the credit memo with the given identifier. Only the fields in the request body change. Use the credit memo's id, not its creditMemoNumber.

[Open in the interactive reference](https://docs.api.lensing.ai/?op=updateCreditMemo)

## Parameters

| Name | In | Type | Required | Description |
| --- | --- | --- | --- | --- |
| `Api-Version` | header | `"v1"` | yes | The API version this request targets, named by its public identifier. Required on every request; omitting it, or naming a version this company does not have, is answered with 400. This document describes version `v1`. |
| `Idempotency-Key` | header | string | no | An opaque caller-chosen string (1-255 characters) that makes this request safe to retry. Repeating the same key with an identical request body replays the original response instead of re-executing - but only once that original request succeeded; a failed attempt re-executes on retry. Repeating the key with a different body is answered with 422. A key still in flight is answered with 409 - as is a key whose original request was interrupted before it finished, for a few minutes afterwards, until that attempt is presumed dead. A completed response stays replayable for 24 hours. The key is scoped to the caller, not to the action: reusing it for a different action is answered with 409 or 422 rather than treated independently. On read actions this header is ignored. On write actions that cannot offer the guarantee it is answered with `400 IDEMPOTENCY_NOT_SUPPORTED` rather than silently ignored. |
| `id` | path | string | yes | The unique identifier for the credit memo to update. |

## Request body

Required, `application/json`: updateCreditMemoInput.

| Field | Type | Required | Description |
| --- | --- | --- | --- |
| `creditMemoDate` | string (date) | no | The new issue date. Use format YYYY-MM-DD. |
| `description` | string | no | The new description. |
| `externalCreditMemoId` | string | no | The new identifier of this credit memo in an external source system. |
| `updateLines` | array of object | no | The line edits, keyed by line id. Only the description can be edited. Lines cannot be added or removed here. |
| `updateLines[].id` | string | yes | The unique identifier for the credit memo line to edit, as returned by GET accounting/credit-memos/:id. |
| `updateLines[].description` | string | no | The new line description, as shown to the customer. On a manual credit memo it cannot be cleared, because a description is required there. |

Example:

```json
{
  "creditMemoDate": "2026-01-15",
  "description": "<description>",
  "externalCreditMemoId": "3fa85f64-5717-4562-b3fc-2c963f66afa6",
  "updateLines": [
    {
      "id": "3fa85f64-5717-4562-b3fc-2c963f66afa6",
      "description": "<description>"
    }
  ]
}
```

## Response

`200` Success

## Response headers

- `Idempotency-Replayed` — Present and `true` only when this response replays a previously stored one for the same Idempotency-Key, rather than reflecting a live execution. Absent on a live response - never sent as `false`.

## Errors

| Code | Status |
| --- | --- |
| `NOT_FOUND` | 400 |
| `LINE_NOT_FOUND` | 400 |
| `LINE_DESCRIPTION_REQUIRED` | 400 |
| `IDEMPOTENCY_KEY_CONFLICT` | 409 |
| `IDEMPOTENCY_PAYLOAD_MISMATCH` | 422 |

## Statuses

- `400` — Invalid request or business failure. Codes: NOT_FOUND, LINE_NOT_FOUND, LINE_DESCRIPTION_REQUIRED
- `401` — Missing or invalid access token
- `403` — Not authorized
- `404` — Not found
- `409` — The Idempotency-Key is still being processed by another request.
- `422` — The Idempotency-Key was already used with a different request payload.
- `429` — Too many requests
- `500` — Internal server error