If you go back to January 2010, make the determination and close out the claim, there's a chance the customer will counter with another claim on transactions in 2009. In that case, you re-analyze the liability based on your new set of facts, and use the 2009 dates to establish when the 60-day period would end, keeping in mind that you've already refunded some money based on the first claim.
You need to keep track of what your customer has done or you'll find yourself paying back money that the customer is liable for.
John S. Burnett
Fighting for Compliance since 1976
Bankers' Threads User #8