# invoices.filesPrepare

Prepare an invoice file upload (PDF, Word, image, CSV, or email up to 20 MB). Supply filename, mimeType, sizeBytes, sha256, and idempotencyKey. Upload unchanged bytes to the returned uploadUrl unless alreadyUploaded is true.

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

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

MCP tool: `accounting_invoices_files_prepare`

## Fields

| Field | Type | Required | Notes |
| --- | --- | --- | --- |
| `filename` | string | Yes | The file's name, including its extension. 1–200 characters. |
| `mimeType` | string | Yes | The file's type, such as image/jpeg or application/pdf. at most 150 characters. |
| `sizeBytes` | integer | Yes | The file's size in bytes. 1 to 20971520. |
| `sha256` | string | Yes | The SHA-256 hash of the file's exact bytes, as 64 lowercase hex characters. SHA-256 hash as 64 lowercase hex 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.filesPrepare \
  -H "Authorization: Bearer $OATMILK_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: $(uuidgen)" \
  -d '{
  "filename": "receipt.pdf",
  "mimeType": "example",
  "sizeBytes": 1,
  "sha256": "9f2b5c1d7e3a4b6c8d0e2f4a6b8c0d2e4f6a8b0c2d4e6f8a0b2c4d6e8f0a2b4c"
}'
```

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