Is there a possibility that if the sort code entered by the employee is wrong, system could verify ?

Summary:

The master data for sort code is maintained centrally within banks and branches, based on industry supplied information.  That data will be valid data, but as individual maintains their own bank details, and it's reasonably common for them to make a mistake.  they either pick the wrong sort code or mistype their bank account number, so a validation that the account exists in the branch specified would cut this down massively.  You put in the details and there is instant validation that the data is correct and your money isn't going to the wrong place.

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