Not strictly true. In practice, most banks will not let you deposit/cash a check that is more than 6 months old (if they notice the date) since the paying bank is under no obligation to honor it. But if they do cash/deposit a stale dated check, it's likely that it would go through just fine since the paying bank probably won't verify the date on the check (unless there aren't sufficient funds in the account). And the checking account agreement probably says that the bank may or may not (at its option) honor a stale check.