Key takeaways
- A Peppol invoice can carry attachments, but the invoice in the legal sense remains the structured UBL file, not the attached PDF.
- The attachment sits in the UBL element cac:AdditionalDocumentReference, which carries the EN 16931 group of additional supporting documents (BG-24).
- You can embed the file in the invoice (BT-125) or point to an external URL (BT-124); embedding guarantees it arrives.
- Peppol BIS Billing 3.0 allows only six embedded formats: PDF, PNG, JPEG, CSV, Excel (xlsx) and OpenDocument (ods).
An attachment, not a stand-in for the invoice
Many businesses moving to Peppol ask the same thing: "And my PDF, where does it go?" The habit runs deep, because for years the invoice was the PDF. With the structured e-invoice, the order of things changes. An e-invoice attachment does exist, but it comes as a complement to a document that has itself become a machine-readable file.
On the Peppol network, the invoice that counts is the UBL file compliant with the Peppol BIS Billing 3.0 profile. That file holds the lines, the VAT breakdown and the totals, and it is what the recipient's software reads and posts to the accounts. An attached PDF is only a copy for the human eye: useful, sometimes reassuring, but with no standing as an invoice on its own. Understanding this hierarchy avoids the main mistake, which is to polish the PDF and neglect the structured data.
Where an attachment sits in a Peppol invoice
The European semantic model EN 16931 provides a dedicated place for documents you want to send with the invoice: the group BG-24, "Additional supporting documents". In the UBL 2.1 syntax adopted by Peppol, that group is expressed by the element cac:AdditionalDocumentReference. It is optional and repeatable: an invoice may carry no attachment, or several.
Each supporting document brings together a reference, a description and, above all, the content itself or a link to that content. These are the four business terms that compliant software fills in for you from the file you drop in.
The fields of a supporting document (BG-24)
The document reference (BT-122)
An identifier, in cbc:ID: purchase order number, contract number or document number.
The description (BT-123)
A readable label, in cbc:DocumentDescription, that says what the document is.
The embedded file (BT-125)
The content base64-encoded in cbc:EmbeddedDocumentBinaryObject, with its media type and filename.
Or the external location (BT-124)
A URL in cac:ExternalReference/cbc:URI, when the document stays hosted elsewhere.
Embed the file or point to a link
EN 16931 leaves two ways to attach the document, and the choice has concrete consequences. Either the file is embedded in the invoice, base64-encoded: it then travels with it and is guaranteed to arrive at the recipient. Or the invoice carries only an external link to a URL: the file stays hosted on your side, and the recipient opens it if they want, when they want, if it is still online.
| Embedded file (BT-125) | External link (BT-124) | |
|---|---|---|
| Travels with the invoice | ||
| Guaranteed to reach the recipient | ||
| Still available if your server goes down | ||
| Adds weight to the transmitted message | ||
| Subject to the list of allowed formats |
The Peppol rule is explicit on this point: attachments must be transmitted together with the invoice. In other words, as soon as a document is genuinely needed for processing, it is better to embed it than to rely on a link. The external link keeps its value for a bulky or public document you would rather not push inside every invoice.
The allowed attachment formats
This is the constraint that surprises most: for an embedded attachment, you cannot attach any file at all. Peppol BIS Billing 3.0 restricts the media type to a closed list of six values, and the validation rule BR-CL-24 rejects everything else. A Word document, a ZIP archive or a TIFF image makes the invoice fail validation.
allowed embedded formats
beyond that, the invoice is rejected
ways to attach
embedded file or external link
EN 16931 group
the additional supporting documents
The six media types accepted for an embedded file are the following:
The embedded formats accepted by Peppol BIS Billing 3.0
PDF
application/pdf, the most common format for a readable copy of the invoice.
PNG and JPEG
image/png and image/jpeg, for a photo or a scanned image.
CSV
text/csv, for tabular detail that can be processed automatically.
Excel workbook (xlsx)
application/vnd.openxmlformats-officedocument.spreadsheetml.sheet.
OpenDocument workbook (ods)
application/vnd.oasis.opendocument.spreadsheet.
Two attributes always accompany the embedded file and are mandatory: the media type (BT-125-1), which announces the format, and the filename (BT-125-2), which names it. A media type consistent with the file's real extension avoids rejections: there is no point labelling a spreadsheet as application/pdf.
Your Peppol invoices, attachments included, without touching the XML
YouInv generates your invoices in the Peppol BIS Billing 3.0 profile, attaches your documents in the right format and sends them over the Peppol network.
What it changes for your invoices
In practice, you never handle the base64 or the UBL tags. You drop in a file, and compliant software encodes it, sets the media type and the name, and checks that the format is one of the six allowed. Your job is limited to attaching the right documents and, above all, to getting the structured data of the invoice right.
One useful reflex remains: attach only what sheds light on the invoice. A purchase order, a measurement sheet, an expense receipt or a service report belong as attachments. A logo, a sales brochure or an unrelated document add weight to the message for nothing, and a message that is too heavy can hit the size limits of an access point or a recipient. The attachment is a targeted complement, not a decoration.
Further reading
- The UBL 2.1 format explained: the structure of the file that carries the attachment.
- Peppol BIS Billing 3.0: what the format contains: the profile that sets the validation rules.
- The EN 16931 standard: the semantic model the BG-24 group comes from.
- E-invoice or PDF: why the structured file prevails over the PDF.
The reference source is authoritative: the Peppol BIS Billing 3.0 documentation published by OpenPeppol.
Can you attach a PDF to a Peppol e-invoice?
Yes. The EN 16931 model provides a group of additional supporting documents (BG-24) that lets you attach a PDF or another file to the invoice. The attached document travels alongside the structured invoice but does not replace it: the invoice in the legal sense remains the UBL file.
Which attachment formats does Peppol accept?
For an embedded attachment, Peppol BIS Billing 3.0 allows only six media types: PDF (application/pdf), PNG (image/png), JPEG (image/jpeg), CSV (text/csv), an Excel workbook (xlsx) and an OpenDocument workbook (ods). Any other file type is rejected by the validation rule BR-CL-24.
Where does the attachment sit in the UBL file?
It sits in the cac:AdditionalDocumentReference element, which carries the BG-24 group of the EN 16931 standard. The file itself is base64-encoded in cbc:EmbeddedDocumentBinaryObject (BT-125), with a mandatory media type (BT-125-1) and filename (BT-125-2).
Should you embed the file or use a link?
Both exist. Embedding the file (BT-125) makes it travel with the invoice, which arrives complete at the recipient. An external link (BT-124) points to a URL, but nothing guarantees the recipient opens it. For an essential document, embedding is the reliable choice.
Is an attachment mandatory on a Peppol invoice?
No. The additional supporting documents group is optional and repeatable. A valid Peppol invoice works perfectly well without an attachment: you add one only when a purchase order, a measurement sheet or a receipt sheds light on the invoice.
