The top three tips for writing a letter of retirement are: keep things straightforward, stay polite, and make sure the company feels appreciated. The latter of these tips is very important because it ends the letter on a positive note, and leaves the reader with a good lasting impression.
It is important to keep a letter of retirement forthright so that is evident from the onset that the intention of the letter is to notify the company of the writer's departure. This is particularly important if the writer is leaving in a haste. Keeping the letter direct allows the process to commence almost immediately after the employer receives the letter.