International · Validation
UK VAT number checker.
Check that a UK VAT registration number has the shape HMRC describes: nine digits, with or without a GB or XI prefix. This is a format check only. To confirm that a business is actually VAT-registered, use the official GOV.UK service.
Short answer: a UK VAT number is 9 digits, sometimes written with GB in front (XI for Northern Ireland goods trade under the Windsor Framework). Government departments use GD plus three digits. A correct shape does not mean the number is registered.
Inputs
Result
Enter a number and press Check.
What this checker tests
HMRC's own design guidance describes a UK VAT registration number as 9 numbers, sometimes with GB at the start, and tells services to strip spaces and the GB before validating. GOV.UK says a trader moving goods under the Windsor Framework needs a number that starts with XI, written in front of the usual number (for example XI 123456789 instead of GB 123456789). HMRC's VAT manual says government departments are recorded under GD followed by a three-digit identifier.
- Standard number: nine digits after any GB or XI prefix. Spaces are ignored.
- GD number: the letters GD and three digits.
- Not checked: HMRC does not publish a check-digit rule on the pages used here, so this tool does not compute one. It will not tell you a number is real.
Format check, not a registration check
The only way to confirm a business is VAT-registered, and to see the name and address held against the number, is the official Check a UK VAT number service. This page never contacts HMRC.
Sources
- HMRC design pattern: VAT registration number (9 digits, optional GB prefix)
- GOV.UK: XI prefix for Windsor Framework trade
- HMRC manual VATGPB9400: GD numbers
Retrieved October 2026. Rules can change; check the issuing authority if a result matters.
FAQ
How many digits is a UK VAT number?
Nine. HMRC describes a UK VAT registration number as 9 numbers, sometimes preceded by GB, for example 123456789 or GB123456789.
What does the XI prefix mean?
GOV.UK says a VAT registration number starting with XI is needed to trade under the Windsor Framework (goods in Northern Ireland). It goes in front of the usual number, for example XI 123456789 instead of GB 123456789.
Can this tool tell me if a VAT number is real?
No. It only checks the shape. To confirm that a number is registered, use the GOV.UK Check a UK VAT number service.
What is a GD number?
HMRC records government departments under a special series starting GD followed by a three-digit identifier. HMRC notes that GD numbers cannot be checked in VIES.
Format only, not a register lookup
This tool tests the structure of the number in your browser. It does not query any register, and a passing result does not show the number was issued or is still active. To confirm that, check a UK VAT number on GOV.UK. Nothing you type is transmitted, stored or logged.