The total amount of money that taxpayers will have to repay is unclear, but congressional estimates offer some clues.
Twice since the health care law was passed Congress has increased the caps for how much people will have to repay. Combined, the two measures are expected to raise more than $40 billion over the next decade, according to Congress' Joint Committee on Taxation.
"I think people will get there," said Livingston, the former IRS official. "They will develop instincts about it the way we all do about any process we go through multiple times. But when it's new, in the early years, this will be a real learning curve."