EU e-invoicing explained: EN 16931, UBL, and what it means for freelancers
By the Billebly team · Published 27 August 2026 · Last updated 28 September 2026
If you've started seeing "EN 16931" or "e-invoicing" mentioned by a client, an accountant, or a tax authority, you're not imagining it - EU countries are rolling out mandatory electronic invoicing on their own timelines, and most of them build on the same European standard. Here's what it actually means, without the acronym soup.
What EN 16931 actually is
EN 16931 is the European standard for the content of an electronic invoice. It exists because of Directive 2014/55/EU (opens in a new tab), which requires public bodies across the EU to receive and process e-invoices that comply with a European standard. The European Committee for Standardization (CEN) wrote that standard in its technical committee CEN/TC 434, and the European Commission published it as the reference in Implementing Decision (EU) 2017/1870 (opens in a new tab).
The standard is a semantic data model: a fixed set of fields an invoice must carry (seller and buyer identifiers, a structured VAT breakdown, totals, currency, and more) so that invoicing software in one country can produce a document another country's software can read and validate automatically. The Commission's decision lists exactly two syntaxes for exchanging it: UBL 2.1 and UN/CEFACT Cross Industry Invoice (CII), both XML formats. UBL is the more common of the two. A PDF is designed to be read by a person; a UBL file is designed to be read by a machine, which is the whole point of e-invoicing mandates: tax authorities and accounting systems can validate and process invoices without a human re-typing anything.
The standard itself is being updated: CEN published a revised EN 16931-1 in May 2026, and according to the European Commission (opens in a new tab), invoices following the 2017 version remain compliant during the migration period.
Where e-invoicing is mandatory
Public-sector invoicing came first: since 2019 (2020 for some regional and local bodies), public bodies in every EU country have had to accept EN 16931 e-invoices, and some governments now require them from suppliers. Dutch central government, for example, doesn't accept a PDF as an e-invoice (opens in a new tab).
Business-to-business mandates are newer and move quickly. As of September 2026:
| Country | What's required | Format |
|---|---|---|
| Italy (opens in a new tab) | All domestic invoices, B2B and B2C, since 1 January 2019, sent through the SdI exchange system | FatturaPA (national format) |
| Belgium (opens in a new tab) | Structured e-invoices between Belgian VAT-registered businesses since 1 January 2026, exchanged over Peppol | Peppol BIS (based on EN 16931) |
| Croatia (opens in a new tab) | Domestic B2B e-invoices for VAT-registered businesses since 1 January 2026; businesses outside VAT must receive them now and issue from 1 January 2027 | EN 16931 with a Croatian extension |
| Germany (opens in a new tab) | Every business must be able to receive e-invoices since 1 January 2025; issuing them is required from 1 January 2027 above €800,000 in turnover, and from 1 January 2028 for everyone. Small businesses under the Kleinunternehmer scheme and invoices of €250 or less are exempt | EN 16931, such as XRechnung or ZUGFeRD |
| France (opens in a new tab) | Since 1 September 2026, every business must be able to receive e-invoices through an approved platform, and large and mid-size companies must issue them; small businesses must issue from 1 September 2027 | Via an approved platform (plateforme agréée) |
| Poland (opens in a new tab) | Invoices through the national KSeF system since 1 February 2026 for the largest taxpayers and 1 April 2026 for everyone else; the smallest businesses join on 1 January 2027 | FA(3), a national schema (neither UBL nor CII) |
| Spain (opens in a new tab) | B2B e-invoicing adopted in Royal Decree 238/2026 (opens in a new tab); the start date depends on a ministerial order that hasn't been published yet | EN 16931 (UBL, CII, EDIFACT, or Facturae) |
| Netherlands (opens in a new tab) | No B2B mandate yet; the government announced in September 2026 that it plans one from 1 July 2030, which still needs legislation | To be decided |
So "the same standard everywhere" is mostly, not entirely, true: Italy and Poland run national formats and systems, and several countries prescribe how an invoice must be delivered, not just what it contains.
At EU level, the VAT in the Digital Age (ViDA) directive, (EU) 2025/516 (opens in a new tab), makes EN 16931 e-invoices and per-transaction digital reporting mandatory for cross-border B2B sales between EU countries from 1 July 2030. Since April 2025 it also lets every EU country introduce its own domestic B2B mandate without first asking the EU for permission, which is why more national deadlines keep appearing.
This is general orientation, not tax advice
E-invoicing mandates, timelines, and exact requirements vary by country and business size, and they change often. Check your own country's rules (or ask an accountant) before assuming what applies to you.
What a compliant e-invoice actually needs
At minimum, EN 16931 expects:
- A real seller and buyer identifier (a VAT number or equivalent), not just a name and address in free text.
- Line items with a proper VAT category per line - standard-rated, zero-rated, reverse-charged (common for cross-border EU B2B), exempt, or outside the scope of VAT entirely - not just a single flat tax percentage.
- The structured totals a machine can sum and validate: net amount, VAT amount per category, and the grand total.
These sit on top of what the EU VAT Directive (Article 226) (opens in a new tab) already requires on any invoice, electronic or not: a sequential invoice number, both parties' details, the VAT rate and amount, and a "Reverse charge" mention when the customer accounts for the VAT. Getting this right by hand, invoice by invoice, is exactly the kind of thing worth automating.
Skip building this yourself
Billebly generates a compliant e-invoice automatically for every invoice you create.
Corrections need the same treatment: credit notes
A regular PDF-and-email workflow usually handles a correction with an email and a revised total. EN 16931 has a dedicated document type for this instead: a credit note, a legally distinct corrective document referencing the original invoice, with its own number. Billebly builds this in too - issue a credit note straight from an invoice (it defaults to mirroring every line, for a full correction), and it's exported in the same EN 16931/UBL format as the invoice it corrects.
How Billebly handles this
Every invoice you create in Billebly is automatically accompanied by a UBL 2.1 XML file structured to EN 16931, attached alongside the regular PDF in the emails your client already gets - no extra step, and nothing extra for a payer to see or download themselves; the PDF is all they need. For your own bookkeeping or your accountant, export every e-invoice you've generated in bulk from Settings → Export. Need to correct one? Issue a credit note in the same format, in a couple of clicks. None of this changes how you actually create an invoice; the compliant document is just there when you need it.
Billebly creates the e-invoice file; it doesn't deliver it through a country's prescribed channel. Where a mandate requires a specific route (Peppol in Belgium, an approved platform in France, KSeF in Poland, or SdI in Italy), you'll still need a provider connected to that channel.
Sources
- Directive 2014/55/EU on electronic invoicing in public procurement (opens in a new tab)
- Commission Implementing Decision (EU) 2017/1870 (EN 16931 and its syntaxes) (opens in a new tab)
- European Commission: the European standard on eInvoicing (opens in a new tab)
- Council Directive (EU) 2025/516 (VAT in the Digital Age) (opens in a new tab)
- Council Directive 2006/112/EC (EU VAT Directive), consolidated text (opens in a new tab)
- National rules: linked from each country in the table above.