Can I add attachments to a Peppol invoice?

by Yaron Verfaillie

July 30, 2025

When companies switch to e-invoicing via Peppol, sooner or later the question comes up: can I send attachments along with an electronic invoice? Think an Excel file, work orders, time records or just a PDF copy of the invoice. The good news: yes, you can. Provided you take into account a number of conditions.

How exactly does it work?

Peppol invoices are sent in a structured format such as UBL (Universal Business Language). Attachments are not sent “separately” like an email, but technically embedded in the XML of the invoice. This is done via base64 encoding, where files such as PDFs or work orders are converted to text so they fit securely into the XML file. Consider:

A PDF version of the invoice for visual inspection
A signed work order
A time record or completion document

The recipient receives everything as one structured package. That’s a big advantage of working with Peppol: communication is completely digital and structured.

What is base64 encryption?

Base64 is a way of translating binary files (such as a PDF or image) into a string of letters and numbers that can be embedded in the XML of the invoice. This ensures that the attachment can be passed securely and correctly within the Peppol network.

The software you use automatically takes care of this conversion. It is therefore important that your service provider or Access Point supports this base64 embedding so that your attachments actually arrive at the recipient and can be properly processed.

What are the restrictions on Peppol attachments?

1. Size Limitation
The total size of the invoice (including attachments) should usually be a maximum of 10 MB. This is a limit used by many Access Points, including Nymus’.

2. File Types:
Only business relevant and technically supported file types may be added. Consider:

PDF, XML, PNG, TXT
XLS(X) can, but not always secure – check with your client beforehand
ZIPs or non-readable formats are often rejected

3. No WeTransfer:
Peppol is not a file-sharing platform. Attachments must be functional and directly linked to the invoice content.

What about a PDF version of the Peppol invoice?

Some companies like to include a PDF for human verification. Technically this is possible, but: Within Peppol, the structured data in the XML is leading, not the PDF.

So the recipient is under no obligation to do anything with the PDF. Think of it as a visual extra, but not as the official document.

So that also means that you do not archive the PDF, but you do archive the UBL since that is the official document.

What if my client requests an attachment?

In that case, it is important that:

Your e-invoicing software (such as Nymus’) supports these attachments
Your Access Point structures them correctly in the UBL
You know which types are allowed by the receiver

At Nymus, for example, we can set certain attachments to be automatically added to invoices based on rules, templates or customer requirements.

The benefits of Peppol with attachments

Sending attachments through Peppol offers several advantages over manual or separate shipments:

1. Everything in one file
The invoice and relevant documents are sent together as one structured package. No more need for separate emails or separate PDFs.

2. Fewer errors and misunderstandings
Because the attachments are linked to the invoice itself, they don’t get lost or disconnected. Your customer always has the right context at hand.

3. Faster processing
Accounting or ERP systems can automatically recognize attachments and link them to the correct invoice. This speeds up processing and reduces manual work.

4. Improved audit trail
All information is in one digital document, providing clear and complete records – useful for audits or internal audits.

5. More professional communication
You show that your billing process is automated and reliable. Especially for clients paying attention to compliance, this is a plus.

What does this mean for your billing process?

Do you need to change your billing process? That depends on your software vendor and how you use Peppol. With the right configuration, you can Peppol attachments automatically, directly from your accounting package.