Via Daily Mail:
The Obama administration said on Friday that the Internal Revenue Service sent incorrect tax information to about 800,000 Americans who enrolled in new medical insurance plans through Healthcare.gov.
The Centers for Medicare and Medicaid Services, the Health and Human Services subagency that handles Obamacare, sent them forms that contained an error which would cause them to miscalculate the government subsidy for their insurance policies.
That, the administration admitted, would change the amount of their tax refunds, or change the amount they owe.
A source at the Treasury Department told Daily Mail Online that of about 80,000 people who have already filed their taxes on the basis of the flawed information, it is expected that 50,000 will have to file again.