Modulus Checking


Modulus checking ensures that account numbers are checked against bank sort codes, helping support the Real Time Information (RTI) initiative introduced by the HMRC to improve the operation of PAYE.

Our Sorting Codes Online product includes a field in sort code search options that allows users to perform modulus checking for account numbers. By populating both the sort code and account number fields users can perform account number validation, as modulus algorithms are determined on a sort code level, obtained from BACS as the issuing source.

Although modulus checking increases the reliability of the data provided, it is only one aspect of account number validation. Modulus checking does not guarantee the actual existence of the account number.

Sorting Codes Online customers can also continue to search by sort code only. The search sort code and account number option is a new feature in addition to the sort code only search.

The acceptable range for account numbers is between six and eight digits. Modulus checking cannot be performed for any account numbers submitted outside this range.

Note, not all financial institutions utilise modulus checking for their account numbers.

What results will modulus checking display?

The validation can provide the following results:

  • Valid account number structure. Passes the defined modulus check for the given financial institution.
  • Account number does not pass the modulus check. The checksum found within the account number does not pass the modulus check for the given financial institution. You should confirm the details before proceeding.
  • Modulus checking cannot be performed.. The financial institution has not made the modulus algorithm publicly known. This does not necessarily mean that the account number is invalid.
  • Account number length is not valid. Please check the length. Account numbers are normally eight digits. If you provide fewer than six digits, you will be asked to correct your input.
  • Account Number padded to correct length. If the account number you provide is six to seven digits long, it will be padded to the correct length with leading zeros.