🕵️‍♀️ How to Spot Fake VAT Numbers: A Guide for UK Businesses

Invoice fraud is a growing threat to UK businesses, with "fake VAT invoices" being a common tactic used by scammers. Paying an invoice with an invalid VAT number doesn't just mean losing money to a fraudster—it also means you cannot reclaim that VAT from HMRC.

If HMRC discovers you've reclaimed VAT on a fake invoice, you are liable to pay it back, plus potential penalties.

Here is how to spot a fake VAT number and protect your business.

1. The Format Check (The "9-Digit" Rule)

UK VAT numbers follow a specific format. The most common format for standard businesses is:

GB 123 4567 89

It always starts with GB.
It is followed by 9 digits.

If an invoice shows a VAT number with 8 digits, 10 digits, or random letters (other than GB), it is immediately suspicious.

Note: There are exceptions for Health Authorities (HA) and Government Departments (GD), but 99% of B2B invoices will follow the 9-digit standard.

2. The "Modulus 97" Check (The Math Trick)

Did you know VAT numbers aren't just random numbers? They follow a mathematical algorithm called the Modulus 97 algorithm.

While you don't need to do the math yourself, knowing this exists is important. Scammers often just type random numbers (e.g., "123456789"), which will fail this mathematical check.

VATextract uses this algorithm instantly on every invoice you upload to flag invalid numbers before you even look at them.

3. Check the Address

A valid VAT invoice must show the supplier's address. A common sign of a fake invoice is:

No address at all.
A PO Box address (often used to hide identity).
An address that doesn't match the company's Companies House record.

Always do a quick Google Maps search if you're unsure. If the "Headquarters" is a residential house or a virtual office, proceed with caution.

4. Use the Official HMRC Checker

The only way to be 100% sure is to check the number against the official registry.

You can use the HMRC VAT Checker for free.

Go to the website.
Type in the 9-digit number.
See if it belongs to the company claiming it.

The Problem: Doing this manually for every single invoice is incredibly time-consuming. Most finance teams only check new suppliers, leaving them vulnerable to existing suppliers who might de-register (or be hacked).

5. Automate the Check

The safest way to protect your business is to validate every single invoice, every time.

Tools like VATextract do this automatically.

When you forward an invoice to us, our AI extracts the VAT number.
We instantly ping the official HMRC and VIES (EU) databases.
We give you a Green Check ✅ if it's valid, or a Red Warning ❌ if it's not.

This happens in seconds, costing you zero extra time but saving you from potentially thousands in fines.

Summary

Don't let a fake invoice slip through the net.

Look for the "GB" and 9 digits.
Check the supplier address.
Verify with HMRC (or let automation do it for you).

Want to check your recent invoices? Try VATextract for free and see if any of your suppliers are flagging up as invalid.