A sort code is a six-digit number that identifies the bank, and often the specific branch, where an account is held in the United Kingdom and the Republic of Ireland. It is usually written as three pairs of digits separated by hyphens, such as 20-00-00. Together with an eight-digit account number, it is the standard way to tell a UK payment system where to send money.
The sort code does a job similar to the American ABA routing number and to the bank-and-branch portion of the basic bank account number used in other countries. It is not the same as a BIC, which identifies a bank on international networks, but it is embedded inside every UK and Irish IBAN.
Sort code in plain terms
A sort code is like the postcode for a bank. When you post a letter, the postcode gets it to the right sorting office and street; the house number then gets it to the right door. In UK banking, the sort code gets the money to the right bank or branch, and the account number gets it to the right customer.
The name comes from exactly that idea. Sort codes were used to sort paper cheques into bundles for each bank and branch, so clerks and later machines knew where each cheque had to go. The cheques are mostly gone, but the number survived as the address for electronic payments.
How sort codes are structured and used
Sort code ranges are allocated to banks and building societies, so the first digits usually show which institution the account belongs to, and the rest identify a branch or processing centre. Many newer banks with no branches use a single sort code for all customers. Sort codes are listed in the Extended Industry Sort Code Directory, maintained by Pay.UK, which records each code's owner, address and which payment schemes it can receive: Bacs, Faster Payments, CHAPS and cheque clearing. Payment firms check this directory before sending, because not every sort code can take every type of payment.
Sort codes are not only for banks. Electronic money institutions and payment institutions that connect to Faster Payments, either directly or through a sponsoring bank, can be allocated sort codes so that their customers receive UK account details. This is how many app-based accounts and payout services give each user a sort code and account number of their own, even when the money is held in a pooled safeguarding account behind the scenes.
A UK IBAN shows how the sort code fits into international formats. It has 22 characters:
| Part | Example | Meaning |
|---|---|---|
| Country code | GB | United Kingdom |
| Check digits | 29 | Validate the whole IBAN |
| Bank code | NWBK | First four letters of the bank's BIC |
| Sort code | 601613 | Bank and branch |
| Account number | 31926819 | Customer account |
Irish IBANs follow the same pattern, with the six-digit Irish national sort code in the same position.
Validation and fraud checks
Before a payment is sent, banks and payment firms check that a sort code and account number pair is plausible using modulus checking, a published set of check-digit rules that catches typing errors. A valid format does not prove the account belongs to the intended person, which is why the UK introduced Confirmation of Payee, a name check described under bank account verification and verification of payee. These checks matter because changed sort codes and account numbers are a classic sign of payment diversion fraud and authorised push payment fraud.
Sort codes also matter when banks merge or close branches. Accounts may be moved to new sort codes, and the old ones are redirected for a period so that Direct Debits and salary payments keep arriving. Switching banks through the Current Account Switch Service carries payments over automatically, a process covered under bank account portability.
Sort codes outside the UK
The term "sort code" is mainly British and Irish. In Ireland the codes remain inside IBANs, but since the move to SEPA customers normally use the IBAN rather than the sort code alone. Other countries use their own bank and branch identifiers: routing numbers in the United States, transit and institution numbers in Canada, BSB numbers in Australia and IFSC codes in India.