# invoices.correctTax

Correct how an issued invoice imported from outside Oatmilk splits its unchanged total into subtotal and sales tax, without voiding it: pass id, expectedRevision, taxes (up to 5 lines of label, rate in percent, and amountMinor; an empty list means no sales tax), a reason of 10 to 500 characters, and an idempotency key. The tax becomes the sum of the lines and the subtotal the total minus that tax, which moves onto the invoice's single line. The total, payments, status, number, dates, and PDF don't change, and the reason and the split before and after are kept in the audit history. Refused for invoices Oatmilk issued (void and duplicate those instead), void or uncollectible invoices, invoices with more than one line or a quantity other than 1, and taxes above the total. Administrator only.

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

Permissions: `accounting:read`, `accounting:write`, `accounting:admin` · Roles: admin · Idempotency key required · Send `expectedRevision`

MCP tool: `accounting_invoices_correct_tax`

## 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. |
| `taxes` | array of objects | Yes | at most 5 items. |
| `taxes[].label` | string | Yes | 1–80 characters. |
| `taxes[].rate` | string | Yes | Matches ^\d{1,3}(?:\.\d{1,4})?$. |
| `taxes[].amountMinor` | string | Yes | An amount in cents (the currency's smallest unit), written as a whole-number string such as "1250" for $12.50. Matches ^\d{1,18}$. |
| `reason` | string | Yes | A short note saying why, kept in the record's history. 10–500 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.correctTax \
  -H "Authorization: Bearer $OATMILK_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: $(uuidgen)" \
  -d '{
  "id": "9a8b7c6d-5e4f-4a3b-8c2d-1e0f9a8b7c6d",
  "expectedRevision": 3,
  "taxes": [
    {
      "label": "example",
      "rate": "13",
      "amountMinor": "1250"
    }
  ],
  "reason": "Synthetic example from the docs"
}'
```

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