 What to do if you find an old, uncashed check sitting in the back of a drawer? Each year, millions of dollars worth of checks go uncashed. If you should find one you haven't cashed, don't be too quick to sign it and drop it into your nearest ATM. There's no guarantee that a bank will accept it. Some banks, for example, won't take checks that are more than six months old. At the same time, an expiration notice, such as void after 90 days, may be easily overlooked at a bank's discretion.