A Resignation Letter is often required when giving formal notice to an employer to inform them that you are leaving the company. It's often stipulated in an Employment Contract because it provides a written record that you chose to leave your job, and that can affect things like employment insurance. Usually two weeks' notice is the standard notice period, but it can be longer depending on the termination clauses in your contract. Aside from being a requirement, giving notice to your boss is important because it can also help ease the transition of your departure, which gives everyone (your boss, co-workers, and new trainees) time to get everything in order before you're gone. This can help ensure you leave on good terms with your boss so they'll give you a good reference. It should also be noted that in many cases, a verbal statement of resignation doesn't suffice as formal notice, and sometimes this could constitute a breach of contract if a written notice is required by your Employment Contract.