To check whether a UK business is VAT registered, use HMRC's free Check a UK VAT number service at gov.uk/check-uk-vat-number. Enter the nine-digit number and the service confirms whether it is valid and shows the name and address the registration belongs to. It takes under a minute, and if you enter your own VAT number at the same time, HMRC gives you dated proof that the check was made.
That last detail matters more than most people realise, because the reason to check a VAT number is rarely curiosity. It is usually money: input tax you are about to reclaim, or a supplier whose paperwork does not quite add up.
Why checking VAT numbers protects your input tax
When you reclaim VAT on a purchase, you are relying on the supplier's invoice being a valid VAT invoice — and a valid VAT invoice needs a genuine VAT registration number. If the number turns out to be invalid, made up, or hijacked from another business, HMRC can disallow your input tax claim. You paid the "VAT" to the supplier; you still lose the reclaim.
This is not a theoretical risk. Missing trader fraud works precisely by charging VAT that is never handed over to HMRC, and HMRC expects businesses to take reasonable steps to know who they are trading with. A dated consultation record from the checker — proof that on a given day you verified the supplier's number and it matched their name — is exactly the kind of evidence that separates an innocent customer from a careless one if a supply chain later turns out to be rotten.
Our rule of thumb for clients: check the VAT number of every new supplier before the first invoice is paid, re-check when invoice details change (new name, new bank account, new address), and keep the proof with the supplier record.
What the HMRC checker shows — and what it doesn't
The service confirms three things: that the number is valid, the business name it is registered to, and the registration address. Cross-check both against the invoice. A valid number with the wrong name is a red flag, not a pass — quoting someone else's VAT number is a classic fraud pattern.
What the checker will not do is search by business name. If you have a company name but no number, you will need to get the number from the supplier — it should be on every VAT invoice they issue — and then verify it. The checker also says nothing about whether the business is trustworthy, solvent or filing its returns; it verifies registration, nothing more.
Reading a UK VAT number
A standard UK VAT number is nine digits, usually shown with a GB prefix: GB followed by 123 4567 89. Some variants exist — branch registrations carry a three-digit suffix, government departments and health authorities have their own formats — but the nine-digit pattern covers almost every commercial supplier you will meet. A "VAT number" with the wrong number of digits, or one that is actually a Companies House registration number (eight characters, which can include letters — NI and SC prefixes are common), fails before you even reach the checker.
Since Brexit, GB numbers no longer appear in the EU's VIES database. To validate an EU supplier's number, use VIES; to validate a UK number, use HMRC's service. Northern Ireland businesses trading in goods under the Protocol use an XI prefix, which VIES does still recognise.
What to do when a number fails the check
First, rule out the boring explanation: a typo, an old invoice template showing a lapsed number, or a very recent registration that has not fed through. Ask the supplier to confirm the number in writing.
If the number still fails, or the name on the registration does not match who you are paying, stop reclaiming input tax on their invoices and query it before the next payment run. A supplier who cannot produce a valid VAT registration but is charging VAT is either badly confused or doing something worse — and neither is a problem you want inside your VAT return. If you have already reclaimed VAT against invoices that now look doubtful, take advice before HMRC finds it first; voluntarily corrected errors are generally treated more gently than discovered ones, though outcomes depend on the behaviour behind the error.
When a business must be registered in the first place
A UK business must register for VAT once taxable turnover in any rolling 12 months passes £90,000 — the application is due within 30 days of the end of the month the threshold was crossed, with registration taking effect from the first day of the second month after. A separate forward-looking test applies where you expect to cross £90,000 in the next 30 days alone: register by the end of that period, effective from the date the expectation arose. And there is no threshold at all for overseas businesses making taxable supplies in the UK. Plenty of businesses also register voluntarily below the threshold to reclaim input VAT or to look established.
The rolling-12-months point catches people out constantly: it is not turnover in your accounting year, it is any 12-month window, checked continuously. A strong quarter can tip a business over months before year-end. If that is where you are heading, our VAT registration service handles the registration, scheme choices and first return — and if the numbers are marginal, it is worth a conversation about timing either way.
Building the check into routine compliance
VAT number verification is one of those controls that costs nothing and only ever matters in hindsight. The businesses that come through supplier fraud enquiries cleanly are the ones with a routine: new supplier → number checked → proof filed → payee details matched to the registration. The ones that struggle are reconstructing what they knew, months later, from email threads.
If your purchase ledger has grown faster than your controls, a short review is cheap insurance — our VAT compliance team does exactly this, alongside VAT health checks that look at the return process end to end. Better an hour of tightening now than an assessment letter later.