# invoices.void

Void an invoice with a reason. Invoices with recorded payments must have those payments removed first. Voided invoices stay on record.

`POST /api/v1/accounting/invoices.void`

Permissions: `accounting:read`, `accounting:write` · Roles: admin, finance · Idempotency key required · Send `expectedRevision` · Destructive: confirm with a person first

MCP tool: `accounting_invoices_void`

## Fields

| Field | Type | Required | Notes |
| --- | --- | --- | --- |
| `id` | string (ID) | Yes | The record's ID. |
| `expectedRevision` | integer | Yes | The record's current revision, from the last time you read it. If someone changed the record since, the request is refused with a conflict so you can reload and check before trying again. at most 9007199254740991; greater than 0. |
| `reason` | string | Yes | A short note saying why, kept in the record's history. 3–500 characters. |
| `idempotencyKey` | string | Yes | Any unique text you generate once per intended change, so a retried request only happens once. Send it as the Idempotency-Key header instead if you prefer; if you send both they must match. 8–200 characters. |

## Example request

```bash
curl https://app.getoatmilk.com/api/v1/accounting/invoices.void \
  -H "Authorization: Bearer $OATMILK_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: $(uuidgen)" \
  -d '{
  "id": "9a8b7c6d-5e4f-4a3b-8c2d-1e0f9a8b7c6d",
  "expectedRevision": 3,
  "reason": "Synthetic example from the docs"
}'
```

Reference page: https://app.getoatmilk.com/docs/api/invoices.void