UK sort code & account number checker
Check a UK sort code and account number together before you pay. The check uses the UK’s official modulus checking rules — the same ones banks and Bacs use — to tell you whether that account number can exist at that sort code.
How UK sort code details are built
20-00-00 | Sort code: six digits identifying the bank and branch |
12345678 | Account number: normally eight digits (6, 7, 9 and 10 digit numbers are converted) |
Frequently asked questions
What is modulus checking?
Every UK bank publishes a rule — a weighted checksum — that its account numbers satisfy. Modulus checking applies the rule for the sort code to the account number. A failure means the number is wrong; a pass means it is a possible number at that branch.
Why does a pass not prove the account exists?
The rule only says the number is well formed for that sort code. Whether someone actually holds that account is known only to the bank. Confirmation of Payee, run by the paying bank, checks the name on the account.
My account number has 9 or 10 digits — will it work?
Yes. Some banks and building societies use longer or shorter numbers; the checker converts them the way the UK rules specify before checking.
Some accounts say "cannot be checked" — why?
A few sort codes have no published rule, and some foreign-currency accounts are exempt from the check. Those are reported as unchecked rather than invalid.
Can I see the bank name from a sort code?
The UK sort code directory is not public, so a bare sort code does not give a bank name here. Enter the account as an IBAN in the IBAN checker to see the bank.
Check bank details from your own app
The same validation is in the FluxRail API — for every country, in one call — and runs automatically on every payout you send.