A personal check will be accepted for up to 6 months after the date written on the check. In practice, many checks are cleared by banks after the 6-month period is up, resulting in people being able to cash checks far after the date they are issued for.
The decision to accept or reject a check that is more than 6 months old lies with the bank and is not dictated by government law. The bank can accept a check at any time, even if it is far past the 6-month mark. Because of this, even though a check may not be accepted by a bank, the check is never technically invalid.