# tax.sources.prepare

Prepare an immutable private PDF or photo company/tax source upload. Returns a signed upload URL; this does not create an expense or run AI.

`POST /api/v1/accounting/tax.sources.prepare`

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

Not available over MCP: Accountants' corrections grant isn't offered over MCP yet: phase 1 is read and comment only.

## Fields

| Field | Type | Required | Notes |
| --- | --- | --- | --- |
| `filename` | string | Yes | The file's name, including its extension. 1–180 characters. |
| `mimeType` | enum | Yes | The file's type, such as image/jpeg or application/pdf. One of: `application/pdf`, `image/jpeg`, `image/png`, `image/webp`, `image/heic`, `image/heif`. |
| `sizeBytes` | integer | Yes | The file's size in bytes. 1 to 52428800. |
| `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/tax.sources.prepare \
  -H "Authorization: Bearer $OATMILK_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: $(uuidgen)" \
  -d '{
  "filename": "receipt.pdf",
  "mimeType": "application/pdf",
  "sizeBytes": 1,
  "sha256": "9f2b5c1d7e3a4b6c8d0e2f4a6b8c0d2e4f6a8b0c2d4e6f8a0b2c4d6e8f0a2b4c"
}'
```

Reference page: https://app.getoatmilk.com/docs/api/tax.sources.prepare