[Your Name] [Your Address] [City, State, ZIP] [Email Address] [Phone Number] [Date] [Recipient's Name] [Recipient's Address] [City, State, ZIP] Subject: Apology for Not Crediting Payment from Prompt Payer Dear [Recipient's Name], I hope this letter finds you well. I am writing to extend my sincerest apologies for the oversight in not crediting your recent payment promptly. As a reliable and prompt payer, your payment should have been acknowledged and credited without delay, and I deeply regret the inconvenience caused to you. Upon thorough investigation, it was determined that an internal clerical error led to the oversight of applying your payment to the appropriate account. Please be assured that we have taken immediate steps to rectify this situation and ensure that such errors do not occur in the future. I understand and acknowledge the frustration and inconvenience this oversight has caused you. Rest assured, we value our esteemed clients like you and strive to maintain the highest level of customer satisfaction. Please accept my heartfelt apologies and be assured that we are committed to resolving this matter promptly. To address this issue, I have personally assigned our senior accounts team to rectify the error, locate your payment, and ensure it is credited to your account as soon as possible. We aim to resolve this matter within [timeframe, e.g., 48 hours] and will keep you updated on the progress. In addition to crediting your payment promptly, I would like to offer you a [compensation, e.g., discount on your next invoice] as a gesture of our apology and appreciation for your understanding. We value your long-standing relationship with our company and want to make it right. Once again, please accept my sincere apologies for any inconvenience caused. Should you have any questions or concerns regarding this matter, please do not hesitate to contact me directly at [your phone number] or [your email address]. Our customer support team is also available at [customer support number or email] and will be more than happy to assist you with any further inquiries. Thank you for your understanding and patience. We truly value your business and are committed to ensuring your satisfaction. Yours sincerely, [Your Name] [Your Title/Position] [Company Name]