Based on 1005.6(b)(3) the customer is liable for any charges that occurred more than 60 days from the transmission of the statement on which the first charge appeared. So if the first statement was May 31st, for example, then you could hold the customer liable for any charges that take place on July 31st and following.
Also note that since the customer did not provide timely notice, you are not required to provide provisional credit in 10 business days or complete your investigation within 90 days.
With respect to VISA/MasterCard, failure to review statements can be considered customer negligence and negate Zero Liability even though it does not negate Reg E liability. Also, if these were all unattended terminals (MCC 5542) you have chargeback rights for up to 120 days after the transaction date so using the chargeback process, you could recover most of the funds.
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