HMRC VRN
The UK VAT registration number issued by HM Revenue and Customs to businesses registered for VAT in Great Britain.
What it is
An HMRC VRN (VAT registration number) is the nine-digit identifier issued by HM Revenue and Customs to a UK-registered business, typically displayed with a GB prefix (for example GB123456789). Northern Ireland businesses trading goods with the EU also receive an XI-prefixed number that remains validatable through VIES.
Where you meet it
You meet HMRC VRNs on UK sales invoices (the supplier VRN is a mandatory field under the Value Added Tax Regulations 1995, reg. 14) and in the public Check a UK VAT number service operated by HMRC at api.service.hmrc.gov.uk/organisations/vat/check-vat-number/lookup/{vrn}. In vatverify, a GB-prefixed number is routed to HMRC's endpoint rather than VIES; the response includes the registered name and address, which surfaces in /v1/validate as the registeredName field.
Two valid lengths
A GB VAT number can be 9 or 12 digits after the prefix:
- 9 digits: standard form, covers the majority of UK businesses.
- 12 digits: branch trader number, the 9-digit root plus a 3-digit branch suffix used by companies with multiple VAT-registered branches.
Validators that hardcode GB\d{9} reject correctly-formatted branch trader numbers. The right pattern accepts both lengths. Two legacy forms also still appear: GBGD### for government departments and GBHA### for health authorities. See the UK page for the full format detail.
Post-Brexit routing
Since 1 January 2021, GB-prefixed VAT numbers are no longer queryable through VIES. The EU Commission removed GB from the VIES system, and HMRC's own API became the authoritative endpoint. Validators that route GB through legacy VIES integrations either return errors or stale results.
XI-prefixed Northern Ireland numbers continue to flow through VIES under the Windsor Framework, because Northern Ireland goods trade with the EU still operates under EU VAT rules. See the Northern Ireland page for the dual-number context.
Common confusions
- Since 1 January 2021, GB VRNs are no longer queryable through VIES. Validating a UK number through VIES after that date returns an error or a cached "invalid" result.
- The 9-digit VRN uses a weighted-checksum algorithm (HMRC's "7-cube" rule with subsequent revisions for numbers above 9,990,000,000), so a typo is caught at format level before the HMRC call.
- A GB VRN does not validate the same way as an XI VRN. They have the same 9-digit numeric structure but route to different registries (HMRC vs VIES) and have different legal effects for VAT purposes.