They are not the only married couple in America who talk about taxes and ulcers in the same sentence. Nor are they the only couple who believe they are paying more than they should. On that ground they are part of a noisy majority.

But they are a couple for whom tax season also entails an identity crisis. You see, Melba Abreu and Beatrice Hernandez file state taxes as what they are — a legally married Massachusetts couple. But under federal law, they have to file federal taxes as what they aren't — two single women.

This identity crisis is not just some psychological blip on the cheerful landscape of their family life. In the last four years, the government's refusal to consider them a married couple has cost the writer and the CFO of a nonprofit about $5,000 a year.

This is one reason they joined seven other married couples and three surviving spouses last month in bringing a legal complaint against DOMA, the law that deliberately denies federal benefits to same-sex marriages. The other plaintiffs include a postal worker who can't get health care coverage for her spouse, a widower ineligible for higher Social Security benefits, and a couple who can't get a passport under their married name.

The suit is not just timely because we all share a certain post-tax traumatic stress syndrome. But we have just doubled the number of states in which same-sex couples can be legally married. First, Iowa joined Massachusetts and Connecticut. Then Vermont followed with the first legislative approval. And a bill was just introduced in New York, where people cringe to find themselves lagging behind Iowa.

This is all part of a careful state-by-state strategy. But as a side effect, it's producing more Americans with a strange dual citizenship: Married in the eyes of Iowa, single in the eyes of Washington. Eligible for a pension, health care, family leave in the eyes of the state; ineligible in the eyes of the feds.

DOMA is doing it. The so-called Defense of Marriage Act passed in the panic of 1996 when it looked as if Hawai'i would become the first state with gay marriage. The purpose was as obvious and discriminatory as Rep. Henry Hyde's declaration that DOMA was to express this "disapprobation" for homosexuality.

The day that it passed, Dean Hara remembers deliberately going to have dinner in the members' lounge with his longtime partner, Rep. Gerry Studds, to face down his colleagues. Now, 13 years later, after their marriage and Studds' death, Hara is denied congressional survivor's annuities of $60,000 a year.

"Gerry worked for the federal government for 25 years," says Hara. "We were legally married. Why am I being treated differently as a surviving spouse?" He brings this question as a plaintiff in the case he describes as a posthumous "love letter to the things Gerry believed in."

Much has changed since 1996. Even Rep. Bob Barr, who wrote DOMA, now disavows it.

GLAD, the gay rights group that brought the marriage case to the Massachusetts court, is arguing on pretty narrow grounds. "In our system," says Mary Bonauto, "the states decide who gets married. It's a violation of equal protection to deny recognition of marriages of same-sex couples validly licensed by their state.

"Our case does not seek to marry any more people," she adds. "It's about how the federal government is dealing with people already married by their states." But this is also a next step, the first direct confrontation with a federal law against gay marriage.

There is still enormous controversy around this issue and setbacks such as Proposition 8 in California. But in the glacial scheme of social change, attitudes are evolving at whitewater speed. Civil unions were once radical, now they are the conservative default position. The scare tactics of 1996 are the satires of 2009.

So what do you say about an out-of-date law that enforces an identity crisis? What do you say about a law that "defends" marriage by denying it? The winds are blowing, but in a very different direction.

Ellen Goodman is a colmnist for The Boston Globe. Reach her at ellengoodman@globe.com.

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