# Attachments to messages Often our customers wants to add, or request, attached documents to their messages, e.g. their invoices. We support all the same attachments as Peppol does: [Peppol media types](https://docs.peppol.eu/poacc/billing/3.0/bis/#media-type) | SUPPORTED FILE TYPES | | | -------------------- | --------------------------------------------------------------------------------------------------------------------------- | | **Do**cuments | application/pdf | | Images | image/png image/jpeg | | Text | text/csv | | Spreadsheet |

application/vnd.openxmlformats-officedocument.spreadsheetml.sheet application/vnd.oasis.opendocument.spreadsheet

| ### Technical details Any attachment has to be `base64` encoded and added under the `AdditionalDocumentReference` element;
JSONXML
{
  "AdditionalDocumentReference": [
    {
      "ID": [
        {
          "_": "InvocieSpecification01"
        }
      ],
      "DocumentType": [
        {
          "_": "Specification"
        }
      ],
      "Attachment": [
        {
          "EmbeddedDocumentBinaryObject": [
            {
              "_": "UjBsR09EbGhjZ0dTQUxNQUFBUUNBRU1tQ1p0dU1GUXhEUzhi",
              "mimeCode": "application/pdf",
              "filename": "InvocieSpecification01.pdf"
            }
          ]
        }
      ]
    }
  ]
}

<cac:AdditionalDocumentReference>
  <cbc:ID>InvocieSpecification01</cbc:ID>
  <cac:Attachment>
    <cbc:EmbeddedDocumentBinaryObject mimeCode="application/pdf" filename="InvocieSpecification01.pdf">UjBsR09EbGhjZ0dTQUxNQUFBUUNBRU1tQ1p0dU1GUXhEUzhi</cbc:EmbeddedDocumentBinaryObject>
  </cac:Attachment>
</cac:AdditionalDocumentReference>