Attachments

Supporting documents (BG-24) such as a timesheet or a drawing travel with the invoice, embedded as base64, or are referenced by URL. Each needs a reference (BT-122). The snippets extend the base invoice.

Embed a file

The content is base64 text with a MIME code from the list Peppol allows and a file name. Encode it with btoa(), which every runtime has; the libraries never use Buffer.

// btoa() exists in Node.js, Bun, Deno and browsers; no Buffer needed.
function toBase64(bytes: Uint8Array): string {
  let binary = '';
  for (const byte of bytes) {
    binary += String.fromCharCode(byte);
  }
  return btoa(binary);
}

const csv = new TextEncoder().encode('date,hours\n2017-11-01,7.5\n');

const embedded: InvoiceInput['additionalDocumentReference'] = [
  {
    id: 'TS-2017-11',
    documentDescription: 'Timesheet November 2017',
    attachment: {
      embeddedDocumentBinaryObject: {
        value: toBase64(csv),
        mimeCode: 'text/csv', // one of the MIME codes Peppol allows
        filename: 'timesheet.csv',
      },
    },
  },
];

Link to a file

const external: InvoiceInput['additionalDocumentReference'] = [
  {
    id: 'DRAWING-7',
    documentDescription: 'Technical drawing',
    attachment: { externalReference: { uri: 'https://supplier.example/drawings/7.pdf' } },
  },
];

A document reference holds either an embedded file or a link, not both.