Skip to main content
Attach invoices, receipts, and supporting documents to your business’s outgoing transactions, including payments, ACH, wires, and transfers between wallets. Files are private to your business; the recipient cannot access them.
Attachments are in early access and subject to change. Contact hi@natural.com for access.

​
Add a document

Send POST /attachments as multipart form data with the outgoing transactionId (txn_*) from your transaction history and the file. Include an Idempotency-Key header.
The file is validated and stored in the same request. The response is the attachment, with its ID (pat_*). A file that is not a valid PDF, PNG, or JPEG is rejected with a 400.

​
View and remove documents

List documents with GET /attachments?transactionId=txn_…. GET /attachments/{attachmentId}/download returns the file itself, with its content type and filename. DELETE /attachments/{attachmentId} removes the attachment. Later downloads return not found.

​
Export document references

Use GET /attachments/export?transactionId=txn_… to get data.filename, data.csvContent, and data.generatedAt. Save csvContent as the named CSV file. The CSV includes document metadata and stable API paths for retrieving each attachment. These paths require authorization; they are not public download links.

​
Access

Attachments belong to the business’s outgoing txn_* and its recorded wallet, regardless of payment rail. Existing read and write permissions apply within that party and wallet scope; read-only callers cannot upload or remove documents. Unpaid Requests are not supported.

​
Limits

Attached files cannot be replaced. To use a different file, create a new attachment. Validation checks file size and format; it does not scan for malware.