Check out Reg E 205.6
3) Periodic statement; timely notice not given. A consumer must report an unauthorized electronic fund transfer that appears on a periodic statement within 60 days of the financial institution's transmittal of the statement to avoid liability for subsequent transfers. If the consumer fails to do so, the consumer's liability shall not exceed the amount of the unauthorized transfers that occur after the close of the 60 days and before notice to the institution, and that the institution establishes would not have occurred had the consumer notified the institution within the 60-day period. When an access device is involved in the unauthorized transfer, the consumer may be liable for other amounts set forth in paragraphs (b)(1) or (b)(2) of this section, as applicable.