According to the IRS, about 15 million Americans may have underpaid the government by around $400 because of confusion with Obama’s "Making Work Pay" tax credit. In a worst case scenario, all 15 million of those taxpayers will have to pay back that $400 on their next tax bill, in one lump sum payment.
One of the groups most affected by the bureaucratic slip-up: married couples.
If you and your spouse both work and earn more than $13,000, each has been credited $200 too much. That means you'll owe Uncle Sam $400 when you file jointly.
The amount owed goes down for couples making more than $150,000 a year because they weren't eligible for as much of the tax credit.
SMU Cox Business School professor Mike Davis explains the plan was intended to add about $33 a month to everyone's paycheck.
