United Kingdom VAT number: format and validation

By Remco from Avatcado

Format

GB followed by 9 or 12 digits. The local term is VAT registration number (VRN, English).

Pattern: /^\d{9}(\d{3})?$/

  • The 12-digit form is the 9-digit VAT number plus a 3-digit branch or subsidiary identifier; conventionally written GB 123 4567 89
  • GB numbers are not in VIES since 1 January 2021; validate via HMRC's checker or the Check a UK VAT Number API
  • Rare GBGD and GBHA forms exist for government departments and health authorities and follow a different pattern

Example of a registered number: GB 823 8476 09

Check digit

United Kingdom VAT numbers carry a check digit (MOD 97 / MOD 9755): Weights 8 down to 2 over the first 7 digits with the last 2 digits as the check; registrations from about November 2009 use the parallel 9755 variant (add 55 before reducing mod 97). Widely documented, though not officially published by HMRC.

Check a United Kingdom VAT number

Checks route through HMRC. Caching is enabled by default. Read the source, original result time and freshness label alongside validity; a cached or stale result does not freshly confirm current registration.

Enter a VAT number to see its registration result, source and freshness

Validate via API

The same validation as an API call, with the example number above:

curl "https://api.avatcado.com/v1/validate?vat_number=GB823847609" \
  -H "Authorization: Bearer avat_live_your_api_key"
import Avatcado from "@avatcado/node";

const avatcado = new Avatcado("avat_live_your_api_key");
const { data, error } = await avatcado.vat.validate({
  vatNumber: "GB823847609",
});

if (data?.data.valid) {
  console.log(`Registered: ${data.data.company?.name}`);
}

Free tier includes 500 validations per month. Get an API key or read the API documentation.

How Avatcado validates United Kingdom numbers

  • Primary source: HMRC.
  • Company name and address: yes.
  • When HMRC is down: the most recent cached result, then a refunded 503.

See the full coverage table.

Frequently asked questions

What is the UK VAT registration threshold?

GBP 90,000 of taxable turnover, in force since 1 April 2024 when it rose from GBP 85,000. Below it, registration is voluntary.

How do I check a UK VAT number since Brexit?

VIES stopped covering GB on 1 January 2021, so use HMRC's free online checker at gov.uk/check-uk-vat-number or the Check a UK VAT Number API, which returns the registered name and address.

What does a 12-digit GB number mean?

It is the standard 9-digit VAT number with a 3-digit suffix identifying a branch or subsidiary trading under the same registration; the first 9 digits alone are the registration.

How does Avatcado validate United Kingdom numbers and what happens when HMRC is down?

Avatcado does not validate United Kingdom numbers through VIES: uncached checks use HMRC. Caching is enabled by default without a requester VAT number, so a result may reflect an earlier lookup. Read its source, original result time and freshness label alongside validity. A confirmed answer includes the registered company name and address, and there is no separate national fallback register behind HMRC for Avatcado to consult if it is unavailable. When HMRC cannot answer because of an outage or timeout, an eligible stored result can be served with meta.cached: true and meta.source_status: "unavailable", plus meta.stale: true when it is past the cache window. Requester checks disable stored responses by default; cache=true opts back in. If no eligible stored result can answer, the request returns a refunded 503. Retain the original result time and resolve unavailable checks separately from invalid registrations.

Related guides

VAT rate in United Kingdom

The standard VAT rate in United Kingdom is 20%. Reduced rates: 5%, 0%. See all United Kingdom VAT rates.

Sources