A good example of an employee retirement letter includes an announcement of the retirement, a formal business tone and a general expression of gratitude or goodwill about the employee's experience working at the company. Retirement letters function as a way to smooth the transition for the retiree and the company.
A retirement letter should be formatted in the style typical to the communications of the company the employee works for, in order to maintain professionalism and respect. However, the content of the letter is more variable. Generally the employee states the date of her retirement and promises to continue working to the same standard up to that date. It is not necessary to state a reason for retirement.
There is room in a retirement letter for reflection and rumination, and it is assumed that bosses and other employees take the time to read what the departing employee wants to express. Usually, executives are expected to answer a retirement letter with some form of positive communication thanking the employee for her time and hard work.
Some employees, upon retirement, find it gratifying to include subtle and apt criticism of their bosses or companies. This is not recommended, as burning bridges is never a prudent strategy, but it does make for some humorous quotes on the subject.