It's common knowledge the U.S. tax code penalizes married couples with two working partners, whether they file jointly or separately. Less understood is there's a similar 'marriage penalty' also built into the Affordable Care Act.

"It's easy now to make yourself significantly worse off if the government thinks you're married than if they think you're not," says Kevin Hassett, director of economic policy studies at AEI.

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Speaking with The Daily Ticker's Aaron Task at The Hamilton Project's conference on "Supporting America's Lower-Middle-Class Families" in Washington earlier this week, Hassett explained:  "If two people don't tell the government that they're co-habiting and married, they can each get free health care [if they qualify for Medicaid]. But if they announce that they're married to the government then they lose it and have to buy it on the exchange."

The marriage penalty under the Affordable Care Act affects couples of all income levels:

?    Poor couples hoping to enroll in Medicaid, which is free and available to more people in states that have expanded the program under the ACA.
?    Working class and middle class couples buying health insurance at healthcare.gov or through their state exchanges and hoping to qualify for a government subsidy.
?    Wealthy couples who will now pay tax surcharges to help fund the program--a 0.9% tax on earnings of $200,000 for singles and $250,000 for couples and a 3.8% on investment income over those same threshholds. Two people earning $200,000 each, for example, would not have to pay either tax but married couples with incomes above those levels would.

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Hassett encourages Americans to go on the healthcare.gov website and play with differrent scenarios to see for thesmelves how this 'marriage penalty' plays out.

While broadly critical of the Affordable Care Act, he sees at least one positive aspect: it could help pave the way for a budget deal between Democrats and Republicans.

"If the budget negotiations are put out of the way until after the next election then we'll have to choose something else to talk about and I think the thing we're most likely to talk about is the Affordable Care Act as it unfolds over the next few months," he says. "If you're a supporter of the Affordable Care Act.... then you don't mind that because you think as it starts to work people will like it and they will celebrate the Democrats victory at the polls next year.  But if you're a Republican and think it's not going to work, then you let it unfold and talk about all the bad things are happening."