United Kingdom VAT number validator
How the VAT number format works
- Format
- GB + 9 or 12 digits
- Example
- GB980780684
Things to watch for
- Branch traders append a 3-digit suffix
- Only format+checksum is checked, not live registration
^GB[0-9]{9}([0-9]{3})?$A UK VAT registration number is the 9-digit — or, for branch-registered traders, 12-digit — identifier HMRC assigns to VAT-registered businesses, always shown with a “GB” prefix on invoices, VIES lookups, and customs paperwork (for example, GB980780684). If you invoice UK customers, register a supplier in your accounting system, or check a partner’s number before an EU B2B transaction, this validator is for you.
Before a VAT number reaches HMRC, a supplier’s ledger, or a VIES query, it’s worth catching typos yourself. A single transposed digit produces a number that looks plausible but fails HMRC’s own check digit rule — and a rejected VIES lookup or a bounced invoice costs more time than a five-second check up front.
How this validator works
This tool checks the “GB” prefix, the digit count, and — critically — runs the real mod-97 checksum HMRC uses to generate valid UK VAT numbers, entirely in your browser. Nothing is sent to a server, there’s no signup, and the result appears the moment you stop typing.
What a pass doesn’t tell you
A pass here means the number is correctly formed — not that it’s currently active. HMRC periodically deregisters or reissues numbers, and only HMRC’s own VAT checker or the EU’s VIES lookup service can confirm live registration status; use the official lookup linked below before treating a number as proof of registration. Branch traders get a 3-digit suffix appended to the base 9 digits, so both the 9-digit and 12-digit forms are valid — if a number fails the checksum, re-check the source document first, since mod-97 catches almost every single-digit typo or swapped pair.
Scope: this page and tool cover UK VAT number format and checksum validation only — not VAT registration, return filing, threshold rules, or reclaiming VAT, which sit outside what a client-side format check can tell you. Use this validator to catch a typo before it reaches HMRC or an invoice; use HMRC or VIES to confirm the number is a live registration.
Content last reviewed 2026-07-07.
VAT number FAQ
What does a UK VAT number look like?
It's always 'GB' followed by 9 digits (e.g. GB980780684), or 12 digits if the business is a branch-registered trader — the extra 3 digits identify the specific branch.
Does a successful check mean the business is currently VAT-registered?
No. This tool only confirms the number is correctly formatted and passes HMRC's mod-97 checksum. To confirm it's live and registered, use HMRC's VAT number checker or the EU's VIES lookup.
Why did a number that looks right fail validation?
The mod-97 checksum failed, which almost always means a digit was mistyped or two digits were swapped when the number was copied. Double-check it against the original invoice or registration document.
What's the 3-digit suffix I sometimes see on UK VAT numbers?
It identifies a specific branch or division of a larger group that has registered separately for VAT under the same parent company.