Dear [Customer's Name], We hope this letter finds you in good health and high spirits. First and foremost, we would like to extend our sincere apologies for the oversight regarding the non-crediting of your payment made on [Date]. As a company that takes great pride in prompt and accurate payment processing, we genuinely regret any inconvenience this may have caused you. Upon discovering the error, we immediately investigated the matter and identified the root cause of the issue. It has come to our attention that despite your timely payment, there was a technical glitch within our system that resulted in the failure to properly credit your account. We deeply apologize for this oversight and assure you that necessary steps have been taken to rectify the situation. Rest assured that the entire outstanding amount, along with any associated late fees or inconveniences that you may have encountered due to our error, will be credited to your account by [Date]. Furthermore, as a token of our appreciation for your prompt payment history and to compensate for any inconvenience you may have faced, we will also be providing you with a [discount/voucher] towards your next purchase with us. We understand that mistakes can occur, but we believe it is our duty to take responsibility for our actions and make amends promptly. Your satisfaction is of utmost importance to us, and we are committed to maintaining the highest level of customer service and integrity. In order to prevent such instances in the future, we have implemented additional checks and balances within our payment processing system. We have also provided additional training to our staff to ensure that proper procedures are followed meticulously, safeguarding against any similar occurrences moving forward. Once again, we deeply regret any inconvenience this may have caused you and assure you that this matter will be promptly resolved. We genuinely appreciate your understanding and patience in this matter. Should you have any further questions or concerns, please do not hesitate to contact our customer service department at [Phone Number] or via email at [Email Address]. Thank you for your continued support and trust in our company. Sincerely, [Your Name] [Your Title] [Company Name]