EN 16931 Explained: What Counts as an E-Invoice in Ireland
staxo team, 2026-09-30
EN 16931 is the European standard that defines what an electronic invoice contains and how software reads it. In Ireland it is the test Revenue applies: an eInvoice is issued, transmitted and received in a structured electronic format that allows automated processing and complies with EN 16931, such as XML. PDF invoices and scanned paper invoices do not qualify, as Revenue states on its page Large corporates for Phase One of VAT modernisation.
The date that brings this to every business is 1 November 2028. From then, all businesses in Ireland must be able to receive structured eInvoices, even if they are not yet required to issue them, according to Revenue's press release Revenue confirms large corporates for Phase One of VAT Modernisation. The PDF you email today stays a valid VAT invoice where your customer has agreed to electronic invoices, and it sits outside the EN 16931 definition.
The standard in one paragraph
CEN, the European standards body, issued EN 16931-1:2017 on 28 June 2017. It is a data model: a list of the core business terms an invoice needs, such as invoice number, issue date, seller VAT identifier, line amounts and the VAT breakdown, with rules on how they fit together. The Commission published its reference and the two approved syntaxes, UBL and UN/CEFACT CII, in Commission Implementing Decision (EU) 2017/1870 of 16 October 2017 on the European standard on electronic invoicing.
Irish public bodies must receive EN 16931 eInvoices, central government from 18 April 2019 and sub-central authorities from 18 April 2020, per the European Commission's page eInvoicing in Ireland. From 1 November 2028, invoices from Phase 1 large corporates to their Irish business customers follow the same standard.
Structured data and a picture of an invoice
A PDF invoice is a picture made for a person, which is why a PDF is not an e-invoice under Revenue's definition. Your customer's software has to guess at "VAT €303.75" with OCR, or someone retypes it, and every retyped figure is a chance for a slipped digit to reach a VAT3. A structured invoice in XML is data: the VAT figure sits in a tagged element stating what it is, its currency and its rate, so the receiving system posts it straight to the right account.
Today, issuing invoices electronically in any format needs the agreement of both parties, with records that are retrievable and carry a reliable audit trail, as Revenue explains in its guidance Other types of VAT invoices: electronic invoicing. So an emailed PDF is fine in 2026 when your customer accepts it.
| Format | Made for | Meets Revenue's eInvoice definition | How the data reaches the books |
|---|---|---|---|
| Scanned paper invoice | People | No | Retyped or read by OCR |
| PDF sent by email | People | No | Retyped or read by OCR |
| Hybrid PDF with embedded XML, such as Factur-X | People and software | Likely where the XML carries full EN 16931 data; Revenue has not said | Software reads the XML part |
| EN 16931 XML in UBL or CII | Software | Yes | Imported directly, line by line |
UBL, CII, Peppol BIS and hybrid formats
UBL (Universal Business Language, from OASIS) and CII (Cross Industry Invoice, from UN/CEFACT) hold the same business terms under different element names. Ireland's public-sector eInvoicing supports both, with Peppol BIS as the primary specification.
Peppol BIS Billing 3.0 is EN 16931 in UBL syntax, with element names inherited from the standard, per the Peppol BIS Billing 3.0 specification. Revenue says the new system will use existing infrastructure including Peppol, working with the Office of Government Procurement as Ireland's Peppol authority, in VAT Modernisation: Implementation of eInvoicing in Ireland. Revenue has promised detailed technical specifications ahead of each phase, and as of 29 September 2026 none have been published.
Hybrid formats such as Factur-X and ZUGFeRD wrap a readable PDF around embedded XML. Sovos expects hybrids to stay acceptable under ViDA where they carry EN 16931 data, in ViDA e-invoicing and digital reporting requirements, though Revenue has not confirmed this for Ireland. France already accepts UBL, CII or hybrid formats, according to the French tax administration's guide I want to understand electronic invoicing.
| Name | What it is | Where an Irish business meets it |
|---|---|---|
| UBL | XML syntax from OASIS | Peppol and public-sector invoices |
| CII | XML syntax from UN/CEFACT | Public-sector invoicing; French and German hybrids |
| Peppol BIS Billing 3.0 | EN 16931 in UBL with Peppol validation rules | Primary specification for Irish public bodies |
| Factur-X or ZUGFeRD | PDF with CII XML embedded | Invoices from French and German suppliers |
The fields an EN 16931 invoice carries
Each field in the model has a business term number, written BT followed by digits. Most match details an Irish VAT invoice already shows, each now in its own labelled slot.
Fields Irish VAT invoices already need
| Detail on an Irish VAT invoice | EN 16931 business term |
|---|---|
| Sequential invoice number | BT-1 Invoice number |
| Date of issue | BT-2 Invoice issue date |
| Your name and VAT number | BT-27 Seller name, BT-31 Seller VAT identifier |
| Customer's name, and VAT number where the customer accounts for the VAT | BT-44 Buyer name, BT-48 Buyer VAT identifier |
| Date of supply | BT-72 Actual delivery date |
| Description, quantity and unit price | BT-153 Item name, BT-129 Invoiced quantity, BT-146 Item net price |
| VAT rate and VAT at each rate | BT-152 Invoiced item VAT rate and the VAT breakdown group |
| Total payable | BT-112 Invoice total amount with VAT |
If your invoices already show all of these, the move is mostly about output: the same facts exported as XML. Phase 1 businesses will also report a subset of that data to Revenue, covered in our article on real-time VAT reporting and the pre-filled VAT3 question. Revenue says tax rates, payment requirements and liability calculations stay unchanged, and our guide to the VAT3 boxes T1, T2, E1, E2, ES1, ES2 and PA1 shows where those amounts land on your return.
New fields under ViDA: bank account and corrections
The EU's VAT in the Digital Age package adds invoice fields for transactions in scope of its digital reporting: the supplier's bank account number or an equivalent identifier and, on a corrective invoice, the sequential number of the original, as summarised in Accountancy Europe's VAT in the Digital Age factsheet. EN 16931 already has slots for both: BT-84 Payment account identifier for your IBAN, and BT-25 Preceding invoice reference for the original number.
ViDA was adopted on 11 March 2025, and its digital reporting for cross-border EU business sales applies from 1 July 2030, per the European Commission's page VAT in the Digital Age (ViDA). From then the customer can no longer refuse an e-invoice for those sales.
Credit notes, corrections and the 15-day rule
A VAT invoice must be issued within the 15 days following the end of the month in which the goods or services were supplied, under the Value-Added Tax Regulations 2010 (S.I. No. 639 of 2010), Regulation 23. For intra-EU supplies, ViDA shortens this to 10 days from the chargeable event from 1 July 2030.
Structured data makes corrections stricter. A sent XML invoice has usually been posted by the customer's system already, so the fix is a credit note: its own document type in EN 16931, pointing back to the original through BT-25.
Picture a Kildare farm supplier that bills 40 bags of feed when 30 were delivered. A credit note for 10 bags quoting the original number lets the customer's software match the two automatically.
Keeping records for six years when invoices are data
VAT records must generally be kept for six years from the date of the transaction, per Revenue's page How long do you keep records for?. With e-invoices the XML file is the invoice, and any PDF view generated from it is a convenience copy.
Keep the XML you send and receive, with its delivery record, searchable by supplier, date and number; a received XML file is what backs your VAT reclaim. Ireland's fixed penalty for non-compliance with invoicing and accounting obligations is €4,000, according to the European Commission's summary of Ireland VAT rules.
A Cork electrician's invoice, before and after
Donal is a VAT-registered sole trader electrician in Ballincollig, County Cork. He rewires the kitchen of a café in Douglas: labour €1,600 and materials €650, so €2,250 before VAT. At the 13.5% rate for most building work, explained in our guide to VAT rates in Ireland for 2026, the VAT is €303.75 and the total is €2,553.75.
Before. Donal emails a PDF made from a Word template, and the café's bookkeeper types every figure into their software by hand. One slipped digit in €303.75 would flow straight into the café's VAT3.
After. Donal's software sends the same invoice as EN 16931 XML in UBL through a Peppol access point: number in BT-1, VAT number in BT-31, the 13.5% rate in BT-152, IBAN in BT-84. The café's system posts it with no typing.
Donal trades only in Ireland, and no issuing date has been announced for businesses like his, according to Revenue's page What is VAT Modernisation?. He still has to receive: if his electrical wholesaler is a Large Corporates Division case, its invoices will arrive as e-invoices from 1 November 2028. Our guide to e-invoicing in Ireland for small businesses sets out every phase, and our page on accounting for sole traders covers the day to day side.
How to check your software produces EN 16931
Export one recent sales invoice and look at what comes out. Five questions tell you where you stand.
- Is there an XML file? Look for an export labelled UBL, CII, Peppol or e-invoice.
- Which syntax? A UBL file opens with an Invoice element in the OASIS UBL namespace; a CII file opens with CrossIndustryInvoice.
- Does it declare the standard? A customisation identifier near the top should name EN 16931, and Peppol BIS Billing 3.0 for Peppol.
- Can it send and receive over Peppol? Sending needs an access point, explained in our Peppol guide for Irish businesses. Receiving means an incoming XML becomes a bill in your books.
- Does it hold your IBAN and link credit notes to invoices? Those are the ViDA fields, BT-84 and BT-25.
What to do now
- Export one invoice from your current software and run the checks above.
- Confirm every invoice shows your VAT number, a sequential number, the supply date and VAT per rate.
- Add your IBAN to your invoice template now.
- Correct sent invoices with credit notes that quote the original number.
- Ask your software provider in writing about EN 16931 and Peppol support before 1 November 2028.
- Set up storage that keeps sent and received XML for six years.
Frequently asked questions
What is EN 16931?
EN 16931 is the European standard for electronic invoicing, issued by CEN on 28 June 2017. It defines the core fields an invoice carries, expressed in one of two XML syntaxes, UBL or CII, and Revenue uses it to define an eInvoice.
Will a PDF invoice still be valid in Ireland after 2028?
A PDF does not meet Revenue's eInvoice definition, so it cannot satisfy an obligation to issue eInvoices. From 1 November 2028 that obligation applies to Phase 1 large corporates for domestic business sales, and no issuing date has been announced for businesses that trade only in Ireland. Until a date applies to you, a PDF works where your customer agrees.
What is the difference between UBL and CII?
Both are XML syntaxes for EN 16931, carrying the same business terms under different element names. UBL comes from OASIS and underpins Peppol BIS Billing 3.0, the primary specification for Irish public bodies. CII comes from UN/CEFACT and is common inside French and German hybrid invoices.
Are hybrid formats like Factur-X accepted in Ireland?
Revenue has not said yet. Advisers expect hybrids to remain acceptable under ViDA where the embedded XML carries full EN 16931 data, and France already accepts them.
Does an e-invoice still need my VAT number and a sequential invoice number?
Yes. EN 16931 has dedicated fields for both, BT-31 for the seller VAT identifier and BT-1 for the invoice number. The details an Irish VAT invoice must show carry straight across into those fields.
How long must I keep e-invoices in Ireland?
VAT records must generally be kept for six years from the date of the transaction, and e-invoices are VAT records. Keep the XML files themselves, sent and received.
An e-invoice is EN 16931 data in UBL or CII, and a PDF is a picture of one. To keep invoices, bills and VAT figures in one place while Revenue publishes the details, you can open a staxo account.