Answer:
Unless the unauthorized transaction is otherwise covered under the issuer's rules, they have to notify you within 60 days of the statement transmittal.
1026.13(b) Billing error notice. A billing error notice is a written notice from a consumer that:
(1) Is received by a creditor at the address disclosed under ยง1026.7(a)(9) or (b)(9), as applicable, no later than 60 days after the creditor transmitted the first periodic statement that reflects the alleged billing error;