Ready to fill out your US taxes? Cool. Got ObamaCare? Not so fast

Staff behind the US government's HealthCare.gov say Americans may have received bungled tax forms from the portal – and should hold off filing them.

The health insurance broker on Friday confirmed that it would have to send out new 1095-A claim forms after approximately 800,000 people received incorrectly calculated forms based on outdated data.

The Center for Medicare and Medicaid Service (CMS) said that around 20 per cent of marketplace filers were given the incorrect forms and 50,000 people had already filed their taxes with the incorrect info.

The 1095-A forms [FAQ PDF] are used by taxpayers who signed up for discounted coverage on the HealthCare.gov marketplace to report their monthly premiums and tax credits related to their healthcare coverage.

The HealthCare.gov site said that while the tax credits listed on the forms were correct, the monthly premium amounts listed on some of the forms were outdated and incorrect, so while tax payments would not be impacted, the forms would not be correctly filled.

"Some forms included the monthly premium amount of the second lowest cost Silver plan for 2015 instead of 2014, which needs to be corrected," the administration said in a a statement.

"The incorrect amount is listed in Part III, Column B of the Form 1095-A."

Officials said the updated forms should be sent out to affected people early next month. The US tax deadline this year is April 15. The US Treasury Department will decide what to do with those who already filed.

The issue is the latest in a string of technical gaffes to have befallen the HealthCare.gov portal since its 2013 launch. From the first days of service the website was beset by problems as users could not access the site. Fallout from the bungled opening led the Obama government to sack its original contractor on the platform.

Last summer, it was found that the site had been breached by a hacker, though no user data was believed to have been accessed. ®