Want to know how to write a retirement letter of resignation? Get the insights you need and free retirement letter template to help guide the way.Include the position title and the last day you intend to work. Remember that a retirement letter is a formal one, which may also go in your employee file. So, be sure to make it as straightforward and formal as possible. Call ASRS for information: In Phoenix, (602) 240-2000, or in Tucson, (520) 239-3100 and toll free elsewhere,.