# Credit invoice

`POST /v1/invoices/{id}/credit-notes`

Creates and books a credit note for a booked invoice, by default for all that is outstanding, and lowers the invoice's outstanding balance. Each call is your own approval of the invoice: Numina does not review it, so make sure a person at your company has checked it or has approved the rules your system books by. Booking is final and cannot be undone through this API. It does not send the credit note; use POST /v1/invoices/{id}/send with the credit note's ID.

Not available to Fuld Service customers (403 `booking_not_available`).

Every successful call books a credit note, so send an `Idempotency-Key` header to retry safely. Two credit notes for the same invoice at once: one gets 409 and nothing is booked for it.

Returns 409 for a draft, an offer or a credit note, and when nothing is outstanding. Returns 400 `validation_error` for an amount above what is outstanding or a date in a closed accounting year.

**Scopes:** any of `invoices:book`, `write:ledger`

## Request

```bash
curl -X POST https://api.numina.app/v1/invoices/550e8400-e29b-41d4-a716-446655440000/credit-notes \
  -H "Authorization: Bearer numi_YOUR_API_KEY" \
  -H "Idempotency-Key: $(uuidgen)" \
  -H "Content-Type: application/json" \
  -d '{
    "date": "2026-11-10",
    "amount": 1250,
    "memo": "string"
  }'
```

## Path parameters

- `id` (string (uuid), required): Invoice ID

## Headers

- `Idempotency-Key` (string, optional): Unique key for this request (max 255 characters). Retrying with the same key and body returns the original response instead of doing the work again. (max 255 chars)

## Body (`application/json`)

- `date` (string, optional): Credit note date in YYYY-MM-DD format (default: today). It must be in an open accounting year. (YYYY-MM-DD)
- `amount` (number, optional): Amount to credit incl. VAT, in the invoice's currency (default: all that is outstanding). It cannot exceed what is outstanding. Lines are credited in proportion. (≥ 0)
- `memo` (string, optional): Note on the credit note (default: the invoice's note) (max 2000 chars)

## Response `201`

The booked credit note

```json
{
  "id": "550e8400-e29b-41d4-a716-446655440000",
  "invoice_number": 1001,
  "type": "invoice",
  "credited_invoice_id": "550e8400-e29b-41d4-a716-446655440000",
  "status": "sent",
  "issue_date": "2026-01-15",
  "due_date": "2026-02-15",
  "contact_id": "550e8400-e29b-41d4-a716-446655440001",
  "contact_name": "Acme ApS",
  "currency": "DKK",
  "subtotal": 10000,
  "vat": 2500,
  "vat_rate": 25,
  "total": 12500,
  "has_mixed_vat": false,
  "outstanding_balance": 12500,
  "outstanding_balance_currency": "DKK",
  "currency_rate": 0,
  "delivery_status": "sent",
  "email_delivery_status": "string",
  "email_sent_at": "string",
  "e_invoice_sent_at": "string",
  "is_overdue": false,
  "payment_state": "open",
  "unmatched_payments_note": "string",
  "items": [
    {
      "unit": "string",
      "vat_account_id": "string",
      "vat_code": "string",
      "sales_account_number": 0,
      "vat_rate": 0,
      "id": "550e8400-e29b-41d4-a716-446655440002",
      "description": "Consulting services",
      "quantity": 10,
      "unit_price": 1000
    }
  ],
  "memo": "Project Q1 delivery",
  "payment_details": {
    "bank_name": "Danske Bank",
    "scheme": "dk-registration-number",
    "clearing_code": "3409",
    "account_number": "0012345678",
    "iban": "DK5030000012345678",
    "swift_bic": "DABADKKK"
  },
  "created_at": "2026-01-15T10:30:00Z"
}
```

## Errors

- `400` Bad Request - Invalid input or validation failed
- `401` Unauthorized - Invalid or missing authentication
- `403` Forbidden - Missing scope, the company is archived, or the company is on Fuld Service
- `404` Not Found - The resource does not exist in this company
- `409` Conflict - The invoice cannot be credited, has nothing outstanding, or is being updated
- `422` Unprocessable Entity - The Idempotency-Key was already used with a different request
- `429` Too Many Requests - Rate limit exceeded
- `500` Internal Server Error

See https://developers.numina.app/errors.md for the error format.