The Treasury Department announced Thursday that couples in legal gay marriages will be treated as married couples when filing federal income taxes, effectively answering a recent query from a Democratic senator.

Treasury Secretary Jacob J. Lew noted in a statement that the rule will apply regardless of whether the filers currently reside in a state that recognizes gay marriages.

“Today’s ruling provides certainty and clear, coherent tax filing guidance for all legally married same-sex couples nationwide. It provides access to benefits, responsibilities and protections under federal tax law that all Americans deserve,” Lew said. “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.”

The policy announced Thursday allows gay couples to file amended returns within the statute of limitations for past tax years, so that they may take advantage of tax preferences that are available to married partners.

The announcement comes two weeks after Sen. Benjamin L. Cardin, D-Md., sent a letter to Lew seeking answers to a series of questions about the ability of gay couples to claim prior years’ tax refunds. The IRS is siding with Cardin in not requiring the couples to file the amended returns.

The administration will not recognize civil unions as if they are marriages for tax purposes, though it seems that nothing would preclude a couple in a civil union from traveling to a jurisdiction allowing gay marriage (even abroad), getting married and then claiming the federal tax status in the future.

“Any same-sex marriage legally entered into in one of the 50 states, the District of Columbia, a U.S. territory, or a foreign country will be covered by the ruling. However, the ruling does not apply to registered domestic partnerships, civil unions, or similar formal relationships recognized under state law,” the Treasury Department release said.