Dear [Customer's Name], I hope this letter finds you well. I am writing to offer my sincerest apologies regarding the recent oversight in not crediting your prompt payment correctly. As a company that prides itself on timely and accurate financial transactions, your satisfaction is of utmost importance to us, and we deeply regret any inconvenience this may have caused. Upon reviewing our records, we understand that you promptly made the payment on [Date] in the amount of [Amount]. However, due to an internal error, the payment was not properly credited to your account. Please be assured that we have identified the issue and taken immediate steps to rectify this mistake. We understand the importance of maintaining a seamless payment process, and we want to assure you that this incident was an isolated occurrence. Our team is currently implementing additional measures to prevent similar errors from happening in the future. We apologize for any frustration or inconvenience you may have experienced as a result of this oversight. To rectify the situation, we have already credited the full payment amount to your account, along with an additional [Amount] as a token of our apology. We believe that this action demonstrates our commitment to excellent customer service and maintaining a positive business relationship with you. Furthermore, we want to assure you that we deeply value your prompt payments and the trust you have placed in our company. It is customers like you who contribute significantly to the growth and success of our business, and we want to express our sincere gratitude for your continued cooperation and support. If you have any questions or concerns, please do not hesitate to reach out to our customer service department at [Phone Number] or [Email]. We are more than willing to address any further inquiries you may have and ensure that the necessary steps are taken to regain your confidence in our payment processes. Once again, we extend our deepest apologies for the oversight in not crediting your payment and any inconvenience caused. We look forward to continuing to serve you with the highest level of professionalism and accuracy in all our future interactions. Thank you for your understanding. Sincerely, [Your Name] [Your Title] [Company Name]