It's a point of confusion: When you give your two weeks' notice at work, are you supposed to hand-deliver (or mail) a letter of resignation at the same time?
Yes and no. According to Charlie Javice, founder of Frank, a company that decodes the complicated process for students applying for financial aid, you should still send a letter of resignation when you quit your job, but it doesn't have to be via snail mail anymore.
Instead, send off a quick email right after you give notice. In it, you should include the full date of your last day and a note that thanks your employer for the work opportunity and the chance to grow your experience and career. (Yes, even if it was the worst experience of your life.)
This way, you have something in writing that confirms you left, but it doesn't require a ton of effort on your part.