UK Sort Code Validator
Check a UK sort code and account number against the modulus rules banks use to catch typing mistakes, and see the working.
A UK account number can be tested against its sort code with the modulus check published by Vocalink. It catches most typing mistakes. A pass means the pair is a possible account. It does not prove the account exists, and this tool does not name the bank. It runs in your browser, so nothing you type is sent anywhere.
Validator
Digits only. Spaces and dashes are ignored. Use the 8-digit account number (6 or 7 digits are padded with zeros). The account number is optional.
The examples are test values from Vocalink's own specification, not real accounts.
Go Deeper
What a Sort Code and Account Number Are
A UK sort code has six digits, usually written as three pairs such as 12-34-56. Together with an account number, normally eight digits, it identifies where a UK payment should go. You need both for domestic payments such as bank transfers and Direct Debits.
The sort code points to a bank and branch, but working out which one needs the industry's sort code directory, which is not open data. This tool therefore does not guess a bank from the digits.
How the Modulus Check Works
Some banks build a check into their account numbers, so the account number is only valid for certain sort codes. Vocalink publishes the rules in its modulus checking specification and a weight table with one entry for each sort code range. To check a pair, the tool:
- Finds the sort code in the weight table. If no range contains it, there is no rule and no check can be made.
- Joins the six sort code digits and eight account digits into one 14-digit number.
- Multiplies each digit by the weight for its position and adds the results. The double alternate method adds the individual digits of each product instead.
- Divides the total by the modulus (10 or 11). A remainder of 0 is a pass.
Some sort codes have two checks, and 14 special cases (called exceptions) change the details. The tool follows all of them. Open "Show the calculation" in a result to see every digit, weight and total.
What a Pass and a Fail Mean
- Pass: the sort code and account number fit together under the published rules. Nothing more.
- Fail: most likely a typo, such as a wrong or swapped digit, a wrong sort code or a missing digit. Recheck against the source.
- No rule: many sort code ranges have no published rule, so the account number cannot be checked. That is not a fault.
- Not a name check: the tool cannot tell you who owns the account. For that, use your bank's payee check when you make the payment.
Faster Payments, Bacs and CHAPS
Whether a sort code can receive each type of payment depends on the bank, which this tool cannot see. Pay.UK's sort code checker uses data updated weekly to show whether a sort code can receive Faster Payments, Bacs Direct Credits and CHAPS payments. In general:
- Faster Payments: near-instant payments, with a scheme maximum of £1 million per payment. Each bank sets its own limits, which are often lower (Pay.UK transaction limits).
- Bacs: a batch system used for salaries and Direct Debits, which normally takes three working days.
- CHAPS: same-day payments of any value, used for high-value transfers such as property purchases.
Paying a UK Account from Abroad
Payments from outside the UK usually need the account's IBAN and the bank's SWIFT/BIC code as well. A UK IBAN has 22 characters and contains the sort code and account number, plus a four-letter bank identifier that depends on the bank. We do not generate IBANs, because a wrong identifier gives an invalid IBAN. Ask the account holder for the IBAN, and check it with our IBAN validator.
The Rules This Tool Uses
The tool uses Vocalink's modulus weight table and specification, version 9.10 (valid from 17 October 2026), with the sort code substitution table. We tested the implementation against all 34 test cases in the specification, and all pass. Three sort code ranges in this version (30-35-35 to 30-35-36, 30-53-69 to 30-53-71 and 30-54-68 to 30-54-69) apply from 17 October 2026, and the tool applies them from that date. Vocalink updates the rules from time to time, and we last checked them on 18 September 2026.
Frequently Asked Questions
What is a UK sort code?
A UK sort code is a six-digit number, usually written as three pairs such as 12-34-56, that points to a bank and branch. You use it with an account number, normally eight digits, to make domestic UK payments such as transfers and Direct Debits.
How do I validate a UK sort code and account number?
Enter the sort code and the account number. The tool looks up the sort code in Vocalink's modulus weight table, multiplies the 14 digits by the weights for that range, adds them up and divides by 10 or 11. A remainder of 0 is a pass. Some ranges have two checks and some have special exceptions, which the tool follows.
Does this tool tell me the bank or branch?
No. Naming a bank and branch needs the industry sort code directory, which is not open data, and guessing from the first digits is unreliable. Pay.UK's sort code checker shows whether a sort code exists and which payment types it can receive.
What does a pass mean?
It means the sort code and account number fit together under the published rules, so the pair is a possible account. It does not confirm that the account exists, who owns it, or that the sort code is live.
Why does my correct account number fail?
The usual causes are a typo, a swapped or missing digit, or a wrong sort code. A few providers use account numbers that are not eight digits, or hold accounts that the rules cannot check. If a pair you are sure of fails, confirm it with the account holder or the bank.
Why does it say there is no modulus rule?
Modulus rules are published only for certain sort code ranges. Many ranges have no rule, so an account number there cannot be checked this way. That is normal and does not mean the details are wrong.
Where do the rules come from?
From Vocalink's published modulus checking specification and weight table, version 9.10 (valid from 17 October 2026), together with its sort code substitution table. The tool passes all 34 test cases in that specification. We last checked the rules on 18 September 2026.
Can I check a 6 or 7 digit account number?
Yes. The specification says to add leading zeros, so a 7-digit number gets one zero and a 6-digit number gets two. Some providers, including NatWest, the Co-operative Bank, Leeds Building Society and Santander, use longer numbers that need a provider-specific step first, and this tool does not check those.
Is my sort code or account number stored or sent anywhere?
No. The check runs entirely in your browser. Nothing you type is sent to a server or saved by this page.
What is the difference between Faster Payments, Bacs and CHAPS?
Faster Payments are near-instant, with a scheme maximum of £1 million per payment and lower limits set by many banks. Bacs is a batch system for salaries and Direct Debits that normally takes three working days. CHAPS makes same-day payments of any value and is used for high-value transfers.
Do I need an IBAN to receive money from abroad?
Usually you need the IBAN and the bank's SWIFT/BIC code as well. A UK IBAN has 22 characters and includes the sort code, the account number and a four-letter bank identifier. This tool does not generate IBANs, because the identifier depends on the bank. Ask the account holder for the IBAN and check it with our IBAN validator.
