I wonder if someone has thought this issue through:
As if tax season isn't stressful enough, gay newlyweds in Massachusetts this year are pondering a new thorny question: Do they check "married" or "single" on federal tax forms?
The federal government wants the gay couples who are married in Massachusetts to file as single. This is a lie, of course, and discrimination as horrendous as counting every black citizen as only 3/5ths of a person was. But filing jointly just means the IRS will eventually catch it, kick the return back, and fine you and charge you interest. So gay couples should just file single, right?
Well, maybe. I can think of at least one area in which the feds may have to recognize the couple's status: itemized deduction of state taxes. Under federal tax law, you can deduct the state taxes you pay. In Massachusetts, spouses are responsible for each other's state tax liabilities (presumably; I am not a Massachusetts lawyer or a tax expert). I can imagine scenarios in which you would pay your spouse's state income tax and would then want to deduct it for federal purposes.
As an example, let's say you make $50,000 a year and owe Massachusetts $2,500 in state income tax. And let's say your same-sex spouse is self-employed, makes $60,000 and owes $3,000 in state income tax. (The numbers don't matter so long as your spouse doesn't have sufficient income tax withheld.) Filing single, you would be able to deduct your $2,500 in state income tax. But what if your spouse is unable or unwilling to pay his or her state income tax, and the Commonwealth of Massachusetts secures an additional payment of $3,000 from you as the spouse via a tax judgment? Can you deduct that state income tax payment for federal income tax purposes? You would still be filing single but deducting your spouse's taxes, which would create a kind of hybrid filing status, "single but married".
When and if this situation arises, will the IRS deny the deduction? It's a valid state law income tax. If you don't pay, Massachusetts can seize and sell your property to satisfy the debt. I suppose a court or the IRS could recharacterize your spouse's tax as tax on your own income, but wouldn't even that legal fiction violate DOMA or some other inane federal law? On the other hand, if the IRS denies the deduction, it would be a triumph of form over economic substance. You would have paid a state income tax that you legally owe, yet unlike everyone else in the country, you can't deduct it.
This scenario might seem kind of far-fetched, but it happens all the time. If I were part of a gay married couple in Massachusetts, I might be tempted to engineer the situation and then bring it to the IRS's attention via a letter attached to my return. It's a plausible position to take under current law, so I can't see that I would be fined for trying it. I might lose, but it would highlight - if it needed to be demonstrated once again - the ridiculous lengths to which America will go just to mistreat gay people.