Married same-sex couples living in all U.S. states can file joint federal tax returns, even if local authorities don't recognize their marriages, the Obama administration said yesterday.

The decision by the Treasury Department implements the Supreme Court's decision in June to overturn part of the federal Defense of Marriage Act, which had forbidden the Internal Revenue Service from letting married homosexual couples file jointly.

The government's decision is a victory for same-sex couples who were married in one of the 13 states or the District of Columbia that recognize such relationships and now live in one of the 37 that don't.

"Today's ruling provides certainty and clear, coherent tax-filing guidance for all legally married same-sex couples nationwide," Treasury Secretary Jacob J. Lew said in a statement yesterday. "This ruling also assures legally married same-sex couples that they can move freely throughout the country knowing that their federal filing status will not change."

Couples with unequal incomes will benefit from the marriage bonuses in the tax code; those with relatively equal incomes will have to pay more. The ruling also will make it easier for spouses to inherit money tax-free.

There are more than 130,000 married, same-sex couples in the United States, according to estimates from the 2010 census. For tax year 2013, they may use the married filing jointly or married filing separately status. They have the option to amend returns filed as long as three years ago and can seek refunds; they aren't required to refile returns if they would pay more.

The decision may cause complications for states that don't recognize same-sex marriages and piggyback their tax rules on the federal system. "There are going to be a lot of state tax attorneys working overtime next week," said Verenda Smith, deputy director at the Federation of Tax Administrators. "This is what everyone has been waiting for. Now states can release their own guidance."

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