Answer:
Reg E requires that you complete your investigation of EFT errors, which would include a domestic ATM dispute, within 10 business days. If you cannot complete your investigation within 10 business days, you can take up to 45 calendar days to complete your investigation provided that you give the customer provisional credit for the amount in dispute. There are specific requirements in Reg E around the required notification to the customer of the provisional credit and notice once you complete your investigation depending on whether you will be reversing the provisional credit or making it final. You can find all of that in 12 CFR 1005.11.