Dear [Customer's Name], We hope this letter finds you in good health. We are writing to offer our sincerest apologies for the accounting error that occurred on your recent invoice. We understand the inconvenience and frustration this may have caused you, and we take full responsibility for our mistake. Our team has thoroughly investigated the matter, identified the source of the error, and taken immediate corrective actions to prevent such issues in the future. The error stemmed from an oversight in our invoicing system, which resulted in an incorrect total amount being charged to your account. We deeply regret any confusion or inconvenience this may have caused you. Our accounting department has rectified the error and updated your invoice accordingly. We value you as a customer and want to assure you that this incident does not reflect our commitment to accuracy and integrity. Our team has undergone additional training to prevent similar errors in the future, and we have implemented a more rigorous system of checks and balances to ensure the highest level of accuracy in all our financial processes. Furthermore, as a gesture of our apology, we have taken the liberty to credit your account with a 10% discount on the affected invoice. This credit will be automatically reflected in your next billing statement. We hope this gesture helps to mitigate any inconvenience caused and demonstrates our dedication to your satisfaction. Please rest assured that we have carefully reviewed and thoroughly revised our accounting practices preventing the recurrence of such errors. We are grateful for your understanding and cooperation as we navigate through this corrective process. We apologize for any distress this accounting error may have caused you. Should you have any further concerns or questions regarding your account, please do not hesitate to contact our customer support team at [phone number] or [email address]. We are here to assist you promptly and rectify any remaining issues. Once again, we sincerely apologize for this oversight and any inconvenience it may have caused. We value your patronage and look forward to serving you with the utmost professionalism and accuracy in the future. Thank you for your understanding. Sincerely, [Your Name] [Your Title/Position] [Company Name] [Contact Information]