Northern Ireland e-invoicing: XI VAT numbers and the 2029 mandate

Northern Ireland businesses are expected to be covered by the UK's e-invoicing mandate in the same way as the rest of the UK. Northern Ireland is part of the UK, UK VAT law applies there, and the government says all VAT invoices must be e-invoices from April 2029. The complication is the Windsor Framework: businesses trading goods with the EU use an XI prefix on their VAT number, and EU rules on goods still apply in Northern Ireland.

Here is what that means for e-invoicing, with the unconfirmed points clearly marked.

XI and GB: one registration, two prefixes

HMRC's guidance says that once you have told HMRC you trade under the Windsor Framework and received its confirmation email, "you'll need to start using the XI prefix before your usual VAT registration number - for example, XI 123456789 instead of GB 123456789."

You are eligible to operate under the Windsor Framework if:

• your goods are located in Northern Ireland at the time of sale
• you receive goods in Northern Ireland from VAT-registered EU businesses for business purposes
• you sell or move goods from Northern Ireland to an EU country

Use of the prefix depends on what you are invoicing and to whom:

Transaction	Prefix on your VAT number	Mandate position
Goods or services to a Great Britain business	GB	In scope from April 2029 (UK VAT invoice)
Goods or services to another Northern Ireland business	GB	In scope (UK VAT invoice)
Supplies to a UK public-sector body	GB	In scope (B2G)
Goods from Northern Ireland to an EU business	XI	Not confirmed: cross-border treatment not announced
Services to an EU business	GB	Not confirmed
Goods or services to the rest of the world	GB	Not confirmed

HMRC's guidance says the XI prefix is not needed for services between Northern Ireland and the EU, for supplies within the UK internal market, or for trade between the UK and the rest of the world.

Invoice content rules that already differ

For goods supplied from Northern Ireland to VAT-registered EU customers, HMRC's manual says a full VAT invoice is required, showing:

• XI as a prefix to your VAT registration number
• your customer's EU VAT number, with its country code
• for new means of transport, a description identifying it as such

The VAT guide adds that where the supply is zero-rated or exempt, the invoice must say why. Northern Ireland businesses also cannot use simplified or retailers' VAT invoices where the customer is from an EU member state.

Any UK e-invoice specification will need to carry these extra details for Northern Ireland to EU goods supplies, if those invoices are in scope. That has not been addressed publicly.

The EU dimension: ViDA

The EU adopted its VAT in the Digital Age package (Council Directive (EU) 2025/516) on 11 March 2025. From 1 July 2030, it requires e-invoicing and near real-time digital reporting for intra-EU B2B transactions.

Under the Windsor Framework, EU VAT rules on goods continue to apply in Northern Ireland. That raises an obvious question: will Northern Ireland businesses selling goods to EU customers fall under ViDA's rules from 2030, in addition to the UK mandate from 2029?

This is not confirmed. Some commentators have suggested Northern Ireland goods trade with the EU is likely to be affected. We have found no HMRC, HM Treasury or European Commission guidance setting out how ViDA will apply in Northern Ireland. Be wary of anyone who presents it as settled.

Peppol and XI numbers

The UK has chosen Peppol: the Tax update 2026 says "the electronic procurement system Peppol will be the core interoperability network for e-invoicing in the UK." Peppol is also widely used in EU countries, so a Northern Ireland business on Peppol can, in principle, reach both UK and EU buyers.

Peppol's identifier scheme for UK VAT numbers is code 9932. How XI-prefixed numbers should be represented in Peppol IDs, and whether a business should register one ID or two, has not been confirmed by HMRC or OpenPeppol. Our Peppol IDs for Northern Ireland guide covers the practical options.

VAT groups with Northern Ireland members

UK VAT groups can include members established in Northern Ireland. HMRC's Notice 700/2 says supplies of goods located in Northern Ireland between group members are only disregarded if both members are established in Northern Ireland, and goods moving from Great Britain to Northern Ireland between members can trigger VAT. See VAT groups and e-invoicing.

What to do now

1. Check whether you are identified under the Windsor Framework and use XI correctly today.
2. Split your invoices into GB domestic, Northern Ireland to EU goods, services and rest of world.
3. Make sure your systems store both prefixes correctly against the same 9-digit number.
4. Ask your software provider how it handles XI numbers and EU-specific invoice fields on Peppol.
5. Watch two timelines: the UK roadmap at Budget 2026 on 28 October 2026, and any HMRC guidance on ViDA and Northern Ireland.

See also who is in scope and the timeline.