Dear [Customer's Name], I hope this letter finds you well. Firstly, let me express my sincerest apologies for the accounting error that occurred on [date]. We understand the inconvenience this might have caused you and rest assured, we take full responsibility for the mistake. At [Company Name], we strive to provide exceptional service, accuracy, and reliability to all our valued customers. Unfortunately, due to an oversight in our accounting department, an error was made which led to incorrect calculations in your account. We have already identified the issue and have taken immediate steps to rectify it. Our team has thoroughly reviewed the transaction records and ascertained the root cause of the error. We deeply regret any confusion or frustration this may have caused you, and we assure you that we are implementing measures to prevent such errors in the future. To rectify the mistake made, we have already initiated the necessary corrective actions. The appropriate adjustments have been made to your account, and you should receive the corrected information in the next few business days. If you notice any further discrepancies or have any questions, please do not hesitate to reach out to our dedicated customer service team at [contact details]. They will be more than happy to assist you and provide any additional information you may require. Additionally, as a token of our sincere apologies for this error, we would like to offer you a [discount, voucher, or coupon code] for your next purchase with us. We highly value your patronage and want to ensure your satisfaction going forward. Again, I would like to apologize for any inconvenience caused by this accounting error. We deeply appreciate your understanding and patience as we resolve this matter. Our team remains committed to delivering the highest level of accuracy and reliability in our financial processes. Thank you for bringing this matter to our attention and allowing us the opportunity to make it right. We value your business and will continue to work hard to regain your trust. Please accept our sincere apologies for any inconvenience caused. Sincerely, [Your Name] [Title/Position] [Company Name]