A problem for the government will be if it charges interest (the 10% annual 2012-2019 collins (3)) they will also have to pay the 10% on all payments after 2012 to Fannie and Freddie, politically this will not be an easy one
For the NWS overpayments, UST should pay 10% interest. This is in-lined with the interest charges to the PSPA loan.