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Modulus checking

Modulus checking ensures that account numbers are checked, helping support the Real Time Information (RTI) initiative introduced by the HMRC to improve the operation of PAYE. has added a field to sort code search options, allowing 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.

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.

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

Modulus checking on uses algorithms obtained from the issuing source Bacs.

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.


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