How To Write A Letter Of Work Completion . Peter had full attendance for the 4 week period, was never late to arrive at agreed times, and happily worked over time on at least. We are pleased to inform you that we have been able to complete the construction work at the site in the desired time. Internship completion letter from www.slideshare.net We have been able to complete this before the deadline of (tell deadline). You may write the letter to the individual or company that provided the service, a collection of people such as a supervisor and her staff, or the honoree's boss. Tips for writing a request letter for work completion certificate decide who you should address.