What is customer master file?

It is nothing to do with the actual double entry but is a file with a record for each customer. There is no 'standard' list of what needs to be recorded for each customer (it is up to the company to decide what information they need) but the sort of things that will be recorded are: The customer address and phone number The name of the contact person at the customer company (if it is a company) The VAT number (if they are VAT registered) Any % discount we give the customer What terms of payment we allow the customer (i.e. do we insist on payment before delivery or do we allow them 30 days credit etc..) What credit limit we set of the customer (i.e. the maximum amount we allow them to buy on credit).