Dear [Recipient's Name], I hope this letter finds you well. I wanted to sincerely apologize for missing the deadline on [project/task name] that was due on [date]. I understand the inconvenience and frustration it may have caused you, and I deeply regret any inconvenience or disruption this may have caused to your plans. When I committed to delivering the project on time, I fully understood the importance and urgency of the deadline. However, due to unforeseen circumstances [provide a brief explanation if possible], I encountered unexpected obstacles that hindered the completion of the task within the agreed-upon timeframe. Please allow me to assure you that this incident is not representative of my work ethic or commitment to meeting deadlines. This unfortunate situation has made me aware of the need for improved planning and better communication on my part. I want to take full responsibility for my actions and the consequences they have caused. I genuinely value our working relationship and the trust you have placed in me. With that said, I am determined to rectify this situation and regain your confidence in my abilities. Moving forward, I have taken additional measures to ensure that such mistakes do not occur again in the future. I have implemented a more robust time management system, acquired the necessary resources required to enhance my workflow, and developed a contingency plan to mitigate any unforeseen circumstances that may arise. I understand that my actions have inconvenienced you and possibly affected your schedule. Therefore, I would be more than willing to discuss options to make the situation right. Whether that involves expediting the completion of the project, providing additional support, or any other suitable arrangements, I am committed to finding a solution that meets your needs and expectations. I sincerely apologize once again for failing to meet the agreed-upon deadline and any negative impact it may have had on you and your plans. I highly value our professional relationship, and I look forward to regaining your trust and confidence in the future. Thank you for your understanding and for taking the time to read this letter. If you have any questions, concerns, or would like to discuss further, please do not hesitate to reach out to me at your convenience. Yours sincerely, [Your Name] [Your Position/Department] [Contact Information]