A letter of apology to customers for the mistake made in a recent collection letter. It explains the cause(s) of such clerical error and informs the customer about the rectification made.
Please accept our sincere apology for the mistake we made in our collection letter dated [date]. It is purely [an accounting] / [an invoicing] / [a clerical] / [a sales] / [a computer] error. We have rectified the amount in our system and confirm your account currently has zero balance. Please ignore the collection letter and do not take it as an insult.
does not happen next time,