Free tool · Check bank details
UK sort code and account number checker
Check that a UK sort code and account number pass the official Vocalink modulus rules, the same check banks and payroll software run before a payment goes out. It runs in your browser, so nothing you type is sent to us.
Uses Vocalink's modulus checking specification, version 9.10 (5 September 2026). We deliberately don't show bank or branch names.
What a modulus check is
UK account numbers aren't random. Most banks build a check into them: multiply each digit of the sort code and account number by a published weight, add the results up, and the total divides exactly by 10 or 11. Vocalink, which runs the infrastructure behind Bacs, publishes those weights for every sort code range that uses them, along with fourteen bank-specific exceptions. This tool implements the whole specification and passes every test case in it, so it applies the same rules as the software banks and Bacs bureaux use.
The point of the check is to catch mistakes. A single mistyped digit or two swapped digits will almost always fail, so it's a quick way to catch a typo before money goes to the wrong place.
What the three results mean
- Passes: the account number could exist at that sort code. It's correctly formed, nothing more.
- Fails: the number can't be a real account at that sort code. It's almost certainly a typo, or the sort code and account number have been mixed up with someone else's.
- Can't be checked: the sort code isn't in Vocalink's modulus tables, or the account is a foreign currency account the rules don't cover. Vocalink's guidance is to treat these as valid, but nothing has been verified, so take more care, not less.
Account numbers that aren't eight digits
The rules are written for eight-digit account numbers. Following the specification, the tool adds leading zeros to six- and seven-digit numbers. For nine-digit Santander numbers, it moves the first digit onto the end of the sort code. Ten-digit numbers are used differently by different banks (NatWest uses the last eight digits, the Co-operative Bank and Leeds Building Society the first eight), so the tool tries both readings and tells you which one passed.
What it can't tell you
A pass is not the same as a verified account. Invoice fraudsters don't send malformed bank details. They send their own real, working account, and it passes every modulus check. The check can't tell you whether the account is open, whose name it's in, or whether it belongs to the supplier you think you're paying.
We also deliberately don't show the bank or branch name for a sort code. That information comes from the industry sort code directory, which is licensed, and a branch name doesn't prove who owns an account anyway. For a real check of the name on an account, use Confirmation of Payee when you set up the payment in your banking app.
Where Paylist comes in
Paylist closes the gap a modulus check leaves open. Businesses list their bank details once, and we verify them: the account name is matched with Confirmation of Payee and every listing is reviewed. When a supplier gives you their Paylist number, you look up details they've proven are theirs instead of trusting what arrived in an email. Paylist doesn't move money. It's how you check before you pay.
Privacy
The modulus tables are built into this page and the check runs entirely in your browser. The sort code and account number you enter aren't sent to Paylist or anyone else, and aren't stored. We count how often the tool is used and whether the check passed, never the numbers themselves.
Frequently asked questions
Does a valid result mean the bank account exists?
No. It means the account number is correctly formed for that sort code and could exist. The check can't tell you whether the account is open or who owns it. Use Confirmation of Payee in your banking app to check the name, or ask the supplier for their verified Paylist listing.
Why does it say my sort code can't be checked?
Not every bank publishes modulus rules, and some sort codes aren't in any range in Vocalink's tables. When that happens there's nothing to check against. Vocalink says to treat these as valid, but it means the number hasn't been checked, not that it's correct.
Can this tool tell me which bank a sort code belongs to?
No, on purpose. Bank and branch names come from the Extended Industry Sorting Code Directory, which has licensing terms we don't take on for a free tool. A branch name also wouldn't tell you who owns the account, which is what matters for fraud.
What if my account number has 7, 9 or 10 digits?
Enter it as it is. Six- and seven-digit numbers are padded with leading zeros. Nine-digit Santander numbers and ten-digit NatWest, Co-operative Bank and Leeds Building Society numbers are converted the way the Vocalink specification describes.
Is my data sent anywhere?
No. The check runs in your browser using tables built into the page. We record that the tool was used and whether the check passed, but never the sort code or account number.
How up to date are the modulus rules?
The tool uses version 9.10 (5 September 2026) of Vocalink's modulus checking specification. Vocalink updates the tables every month or two, mainly to add new sort code ranges, and we update the tool when they do.
A supplier's new bank details pass. Are they safe to pay?
Not on that basis alone. Fraudsters use real, working accounts, which pass the check. Confirm any change of bank details with the supplier on a phone number you already hold, not one from the email, or look them up on Paylist.
Check before you pay — every time
Paylist is a verified directory of UK business bank details. Your suppliers list theirs once, and you look them up instead of trusting an email.