Uncashed checks written from banks in the United States are generally valid for 180 days, unless otherwise noted. However, some banks may choose to honor even older checks at their discretion.
Under the Uniform Commercial Code (UCC), U.S.-based banks are not legally obligated to cash checks older than six months. If a person has an old check in his register that still has not cleared, it is best to account for it in his check register, as it could otherwise cause an overdraft when it resurfaces. Likewise, if he is in possession of an old check written to him, he should contact the issuer if more than six months has passed to have it reissued rather than risk it being returned.