Bear with me while I review this more closely.
To be 100% certain on the amount that would be a cost or attributable to the government, we would have to know, for starters, how many people would be non-compliant in this regime.
If there are a large number of people who are non-compliant, and we are in fact charging them less interest, then the government would have less money coming in. On the other hand, if there are a lot of people who are expecting refunds, and we are paying more refunds to those people, then the net effect of the two would be, in fact, a cost to the government.
Without having numbers or estimates, at present, on the compliance and the refund position that taxpayers are in under this statute, we're really not in a position to be certain.