Today, the IRS and the Treasury Department announced that they will treat any same-sex couple married by any state as married, even if they currently live in a state that doesn't have gay marriage.
I know what you're thinking: How will this affect the federal budget?
Over the long term, this decision will increase federal tax receipts by a little. But this year, the federal government may actually lose a little revenue.
Some married couples face a "marriage penalty," meaning they owe more taxes than if they were single, while others get a "marriage bonus." But the penalty effect is more important. Back in 2004, the Congressional Budget Office estimated that gay marriage would mean about $700 million a year in added tax revenues. In practice, because of tax policy changes since 2004, the added revenues would likely be somewhat less.
But one key component of today's announcement is that the IRS will accept amended tax returns from gay couples going back as far as 2010. If you filed previous years' taxes as single because the IRS didn't recognize your marriage, you can go back and change old tax returns to say you're married—but only if you want to.
Gay couples will presumably only take this option if doing so gets them a tax refund. Typically, that would happen for one of two reasons. If the spouses had highly unequal incomes, it's likely they missed out on a marriage bonus, because graduated tax brackets kick in at higher levels for couples than singles. Or, if one spouse put the other on his or her employer-provided health plan in previous years, amending old returns will allow the couple to deduct the cost of that spousal health benefit from tax.
Since only couples getting refund checks will be likely to amend, the IRS decision is likely to cause a short-run revenue loss. But it will be made up in the future, when same-sex married couples have to file their taxes as married whether they want to or not.
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