Dear [Manager's Name],

I am writing to apologize for the delay in delivering the research report for your company.I am working diligently to complete the report as soon as possible and will ensure that it is delivered to you at the earliest.I understand that this report is important to your company, and I assure you that I will do everything in my power to ensure that it is delivered to you in a timely manner.I had to travel out of town and was unable to work on the report during that time.