# Check for duplicate uploads

Required scopes: incoming-invoice:read

Verifies whether a file has already been uploaded by comparing its MD5 hash
against existing document hashes. You may either upload the file directly
(the server computes the hash) or provide a pre-computed MD5 hash string.

Endpoint: POST /incoming-invoices/check-duplicate
Version: v1
Security: http, oauth2

## Request fields (multipart/form-data):

  - `hash` (string)
    Pre-computed MD5 hash of the file – mutually exclusive with file

  - `file` (string)
    PDF or image file to check – mutually exclusive with hash

## Response 200 fields (application/json):

  - `hash` (string, required)

  - `exists` (boolean, required)

  - `duplicates` (array, required)

  - `duplicates.id` (string, required)

  - `duplicates.title` (string, required)

  - `duplicates.invoice_number` (string,null, required)

  - `duplicates.supplier` (object,null, required)

  - `duplicates.supplier.name` (string, required)

  - `duplicates.status` (any, required)

  - `duplicates.booked_at` (string,null, required)

## Response 401 fields (application/json):

  - `message` (string, required)
    Error overview.

## Response 422 fields (application/json):

  - `message` (string, required)
    Errors overview.

  - `errors` (object, required)
    A detailed description of each field that failed validation.