Wording for "Letter of Completion"

[LaBam]

I’m in need of help here. I’ve applied for a job and have almost got the appointment. But my prospective employer is asking that I present them with LETTER OF COMPLETION for each and every project I have undertaken. I’ve approached my past clients and they are willing to give me these if only I could help them with the wording of the said document.

So can anyone please help me with a sample of how such documents are written best?