Since Brexit, the United Kingdom has left the EU VAT system, fundamentally changing how UK VAT numbers are validated and how EU-UK trade is treated for VAT purposes. However, Northern Ireland retains special status for goods, creating a dual system that requires understanding. This guide explains how to validate UK VAT numbers, the XI prefix for Northern Ireland, and the implications of the Windsor Framework.
The standard UK VAT number follows this format:
GB + 9 digits or GB + 12 digits (branches)
Examples: GB123456789, GB123456789012 (branch)
Special formats exist for government departments (GBGD + 3 digits) and health authorities (GBHA + 3 digits), but these are uncommon in commercial transactions.
Since January 1, 2021, UK VAT numbers (GB prefix) cannot be validated through VIES. The EU's VAT Information Exchange System only covers EU member states, and the UK is no longer part of this system. Attempting to validate a GB number through VIES will return an invalid result regardless of whether the number is actually registered.
To validate UK VAT numbers, you must use the UK Government's official VAT number checker:
UK Government VAT Number Checker →
This service confirms whether a GB VAT number is valid and returns the registered business name and address. It functions similarly to VIES but is operated by HMRC (His Majesty's Revenue and Customs) for UK registrations only.
Northern Ireland has special status under the Windsor Framework (successor to the Northern Ireland Protocol). For trade in goods with the EU, Northern Ireland remains aligned with EU VAT rules. This creates a unique situation requiring a separate VAT identifier.
XI + 9 digits
Example: XI123456789
Northern Ireland businesses trading goods with the EU receive an XI-prefixed VAT number in addition to their standard GB number. The XI number can be validated through VIES because Northern Ireland remains in the EU VAT area for goods purposes.
The Windsor Framework, agreed in February 2023, refined the arrangements for Northern Ireland's position between the UK and EU. Key points for VAT purposes:
Goods moving between Northern Ireland and EU member states are treated as intra-community movements, not imports/exports. This means standard EU VAT rules apply, including zero-rating for B2B supplies with valid VAT numbers, reverse charge for the buyer, and no customs duties for goods meeting origin requirements.
Services are treated under UK VAT rules regardless of whether the supplier or customer is in Northern Ireland. There is no XI number requirement for services—use standard GB numbers and apply UK VAT rules.
Goods moving from Great Britain (England, Scotland, Wales) to Northern Ireland face special rules depending on whether they are "at risk" of entering the EU market. The UK Trader Scheme and other mechanisms determine treatment.
XI VAT numbers can be validated through VIES just like any EU VAT number. When you validate an XI number:
Not all Northern Ireland businesses have XI numbers. Only those that have applied for and received XI registration for goods trade with the EU will have them. A Northern Ireland business may have only a GB number if they do not trade goods with the EU.
Understanding the correct VAT treatment depends on the nature of the transaction:
This is an export from the EU. Zero-rate the supply as an export, obtain proof of export, and the UK customer will pay import VAT when the goods enter the UK.
If the NI business has a valid XI number, treat as an intra-community supply. Zero-rate with the XI number on the invoice, and the customer applies reverse charge.
This is an import into the EU. The EU customer pays import VAT on entry. The UK supplier treats it as a zero-rated export.
With valid XI registration, treat as an intra-community supply. The NI supplier zero-rates using their XI number, and the EU customer applies reverse charge.
For all UK-EU services, apply standard international services rules based on the place of supply. B2B services are generally reverse-charged by the customer. Use GB numbers for all UK businesses including those in Northern Ireland.
Remember that GB numbers do not work in VIES post-Brexit. If you need to validate a UK VAT number, use the UK Government checker, not VIES.
Determine whether your Northern Ireland trading partner has an XI number. If yes, you can treat goods trade like intra-EU trade. If they only have GB, you may need to treat the transaction as an export/import.
The XI system applies only to goods. For services, all UK transactions (including Northern Ireland) follow standard UK rules and use GB numbers.
For reference:
