E-invoice validator: Peppol BIS Billing 3.0 and EN 16931
Upload a UBL or CII e-invoice: the validator checks its format, applies the official rules of the European standard EN 16931 and of Peppol BIS Billing 3.0, and reviews the key invoice data. Free, instant, and the file is not stored.
UBL or CII XML file, or PDF with embedded XML (Factur-X / ZUGFeRD), 4 MB maximum
What the validator checks
Today, no UK business has to issue structured e-invoices: an electronic invoice, including a PDF sent by email, is valid if your customer agrees to receive invoices electronically (VAT Notice 700/63). Public buyers must accept and process e-invoices that follow the European standard EN 16931 (Procurement Act 2023), and the NHS uses Peppol.
The government has announced that all VAT invoices will have to be e-invoices from April 2029, with Peppol as the core network. This is an announcement, not yet a law: the format has not been officially fixed, and the roadmap is expected at the Budget of 28 October 2026.
The validator reads the file, recognises its syntax (UBL or CII) and profile, then applies the official rule sets: EN 16931 (mandatory data, calculations, code lists) and, for UBL invoices, the Peppol BIS Billing 3.0 rules published by OpenPeppol. A CII invoice is checked against EN 16931 only, because Peppol BIS Billing 3.0 uses UBL.
It also checks the invoice number and date, the seller's VAT number, the due date and the consistency of the net, VAT and gross amounts. Each point is explained, with how to fix it. The file is analysed in memory and not stored.
- Compliant: the check passed.
- To review: nothing blocking, but a point deserves your attention.
- Error: the invoice breaks an official rule and should be corrected before it is sent.
- The validator is not a certification: your Peppol access point and your customer run their own checks.
Official sources
- OpenPeppol — Peppol BIS Billing 3.0
- OpenPeppol — Peppol BIS Billing 3.0 rules for UBL
- GOV.UK — VAT Notice 700/63: electronic invoicing
- GOV.UK — Procurement Act 2023 guidance: electronic invoicing and payment
- GOV.UK — Promoting electronic invoicing: consultation response (26 November 2025)
- GOV.UK — Tax update 2026: simplification, modernisation and fairness (Peppol)
Rules checked on 20 October 2026. Free tool for information only: it is not legal or tax advice. The rules are checked against the official sources listed on this page; check your own situation before acting.
Frequently asked questions
Is a PDF invoice still valid in the UK?
Yes. A PDF sent by email is a valid invoice if your customer agrees to receive invoices electronically. The April 2029 e-invoicing requirement is an announcement; no law sets it yet.
Which files can I check?
A UBL or CII XML file, or a PDF with embedded XML (Factur-X / ZUGFeRD), up to 4 MB. A plain PDF is reported as not being a structured e-invoice.
Why is my CII invoice not checked against Peppol rules?
Peppol BIS Billing 3.0 is defined in UBL. A CII invoice is checked against the European standard EN 16931 only.
Is my file stored?
No. It is analysed in memory and then discarded. If you ask for the report by email, only the invoice data needed to rebuild the report is sent, then discarded too.
What do codes like BR-CO-15 or PEPPOL-EN16931-R001 mean?
They are the identifiers of the official rules: BR-… rules come from EN 16931, PEPPOL-… rules from Peppol BIS Billing 3.0. Give them to your software provider: they say exactly what to fix.
Further reading
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