If you've made the often difficult and weighty decision to resign or retire, in most cases you must put your intentions in writing. Besides breaking the news, the letter also cites the main reasons behind your decision. It is a common courtesy to the employer to express these intentions to allow the company time to prepare for your departure.
Identify your intention to leave the company immediately in the first line of the letter. Define whether this is a resignation or retirement. For instance, a simple, "I am writing this letter to inform you of my decision to resign from my position as sales assistant to John Smith."
Enter the exact effective date of your departure. Give the company ample notice of at least two weeks. Even if it is not a condition of your employment contract, if you're resigning and planning to seek employment at another firm, you should leave a positive impression at your old firm. New employers commonly call old employers to ask about your work and reasons for leaving.
Discuss the cause of your departure. Use general reasons, such as "I am pursuing a new career" or "I am pursuing new opportunities." Avoid bringing up negative issues from the job that may have prompted your decision, such as a bad experience with a manager. Again, you must keep the importance of leaving a positive impression on the company managers in mind in case you need a referral in the future.
Discuss how grateful you are to have worked for the company to close the letter. It is your decision whether you want to offer to help train your replacement here also. If you want human resources to know your future plans, you can go into more detail in the letter.
Provide your phone number and ask the Human Resources manager to contact you to discuss final issues, such as the date of your exit interview. If you're retiring, request contact regarding your retirement benefits from the company's benefits administration department.