5 common e-invoicing mistakes (and how to avoid them)

The pitfalls of electronic invoicing

Switching to electronic invoicing is an important step for any business. But between UBL format, the PEPPOL network and legal obligations, it’s easy to make mistakes that can cost time and money.

Here are the 5 most common mistakes we see among our users — and most importantly, how to avoid them.

Mistake #1: Confusing PDF with electronic invoice

This is the most widespread mistake. Many businesses think that sending a PDF by email constitutes an electronic invoice. It doesn’t.

Why it’s a problem

A PDF is an “image” of an invoice. It doesn’t contain structured data that accounting software can process. For Belgian legal obligations (B2G since 2024, B2B from 2026), only a structured format like UBL, transmitted via PEPPOL, is considered a compliant electronic invoice.

How to avoid it

Use PEPPOL-compatible software like Digiposapp that automatically generates invoices in UBL format.

Mistake #2: Not checking the recipient’s PEPPOL registration

You’ve set everything up on your end, you send your first invoice via PEPPOL… and it comes back with an error. The reason? Your client isn’t registered on the PEPPOL network yet.

How to avoid it

Before sending an invoice, check that your client is registered on PEPPOL. In Digiposapp, an automatic search tells you whether the recipient is found on the network.

Tip: With the 2026 B2B obligation approaching, more and more businesses are registering on PEPPOL every week.

Mistake #3: Forgetting mandatory fields

A UBL electronic invoice must contain certain mandatory information. An omission leads to automatic rejection.

The most commonly forgotten fields

• VAT number of sender and recipient
• Purchase order reference (mandatory for B2G invoices)
• Currency code (EUR for Belgium)
• VAT rates detailed per invoice line
• Unit of measure for invoiced quantities

How to avoid it

Digiposapp performs real-time validation: if information is missing, you are warned before sending.

Mistake #4: Neglecting credit notes

Electronic credit notes follow the same rules as invoices.

Rules to follow

• The credit note must be in the same format as the invoice (UBL via PEPPOL)
• It must reference the original invoice (number and date)
• The amount must be consistent with the original invoice
• It must be sent to the same PEPPOL recipient

How to avoid it

In Digiposapp, create credit notes directly from the original invoice. The software automatically fills in the references.

Mistake #5: Neglecting archiving

Sending an invoice via PEPPOL doesn’t mean it’s archived. Legal archiving of electronic invoices is a separate obligation.

What the law says

In Belgium, electronic invoices must be kept for 7 years (10 years for real estate). Archiving must guarantee:

• Authenticity of origin
• Integrity of content
• Readability throughout the retention period

How to avoid it

Digiposapp automatically stores all your invoices (sent and received) with their original UBL format, accessible at any time from your account.

Summary

Mistake	Solution
Confusing PDF with e-invoice	Use PEPPOL-compatible software
Recipient not registered	Check registration before sending
Missing mandatory fields	Automatic validation before sending
Poorly managed credit notes	Create from original invoice
Neglected archiving	Integrated automatic archiving

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Avoid these mistakes from the start with Digiposapp. Simple, compliant and secure.

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