UK VAT Number Validator
Enter a UK VAT number, with or without the GB prefix and spaces, to check its check digits against the official HMRC modulus-97 algorithm. Both the standard and the newer 9755 method are handled.
Processed entirely in your browser. This validator runs on your device using JavaScript. The number you enter is never sent to a server, stored, or logged, and nothing leaves your device.
How It Works
A UK VAT number is nine digits, and the last two of those are check digits calculated from the first seven. That built-in relationship is what lets a checker spot a wrong or swapped digit without contacting HMRC. Some organisations, such as branch traders, have a 12-digit version where the extra three digits are a branch identifier.
The check is a weighted modulus-97 sum. Each of the first seven digits is multiplied by a fixed weight, from 8 down to 2. Those products are added together, and the two check digits are added on as a two-digit number. The total is then divided by 97. Under the original rule the number is valid if the remainder is 0. A second rule, known as the 9755 method and used for newer registrations, accepts a remainder of 55 instead. This tool applies both and treats the number as valid if either one is satisfied.
Worked Example
Take the sample number GB 980 7806 84, which is an example rather than a real registration. Multiplying the first seven digits 9, 8, 0, 7, 8, 0, 6 by the weights 8, 7, 6, 5, 4, 3, 2 gives 72, 56, 0, 35, 32, 0, 12, which add up to 207. Adding the check digits as the number 84 gives 291. Since 291 is exactly 3 times 97, dividing by 97 leaves a remainder of 0, so the number passes the standard check.
When You Would Use This
Businesses need a supplier's VAT number to be correct before they reclaim the VAT on a purchase, and a wrong number on an invoice can hold up an accounts payable run or a VAT return. Pasting the number here is a fast first check that the digits are internally consistent, so an obvious typo is caught before the paperwork goes any further. For the final confirmation that the number belongs to a registered trader, the HMRC lookup service is the authority.
Frequently Asked Questions
What does this checker actually verify?
It runs the check digit maths that HMRC built into every UK VAT number. Passing means the number is internally consistent and correctly formed, which catches almost every typo. It does not tell you whether the number is registered to a trading business.
Does a valid number mean the business is VAT registered?
No. The check only proves the digits are mathematically consistent. To confirm a number belongs to a real, currently registered business, use HMRC's official "Check a UK VAT number" service, which looks the number up against the live register.
Can I paste it with GB and spaces?
Yes. The tool removes spaces and an optional leading GB before checking, so GB 123 4567 89 and 123456789 are treated the same. UK VAT numbers are often printed in a 3, 4, 2 grouping for readability.
What is the difference between the standard and 9755 methods?
They are two versions of the same modulus-97 check. Older registrations pass with the original rule, while registrations from late 2009 onward pass with the 9755 variant. This tool tries both and accepts the number if either one passes.
What about 12-digit VAT numbers?
Those belong to branch traders. The first 9 digits are the VAT number and carry the check digits, and the final 3 are a branch identifier. This tool checks the 9-digit core and shows the branch code separately.
Why does my number fail when it is printed on an invoice?
The most common reasons are a mistyped digit or that the number is not actually a GB VAT number, for example an EU VAT number from another country, which uses a different format and check. Double check the digits against the source document.