While the IRS generally hasn’t looked at all returns within the three-year statute of limitations when people amend for a particular year, they could, Miller said.

“That’s why a lot of people are waiting for guidance,” she said.

Court Decision

The U.S. high court struck down the core of the 1996 Defense of Marriage Act, which defined marriage as a union between a man and a woman. The decision didn’t legalize same-sex marriage nationally, leaving regulators to answer questions about residency and retroactivity as it applies to federal tax returns, refunds and benefits.

Same-sex married couples’ finances were complicated by DOMA. They were able to file jointly in states that recognized gay marriages while having to file individual federal tax returns because the U.S. government treated them as single. The division between federal and state law also affected employee benefits, estates and transfers of assets between spouses.

There are more than 130,000 married, same-sex couples in the U.S., according to estimates from the 2010 Census. They have the right to marry in 13 states and the District of Columbia.

Health Benefits

A primary reason for same-sex couples to amend their returns may be if an individual received employer-provided health coverage for a spouse and was required to include the value of that insurance as income, and pay taxes on it, which other married couples weren’t required to do, said Derek Dorn, a partner at Davis & Harman LLP in Washington.

In that case, people may want to wait and see if the IRS will require them to change their filing status to married, which could trigger higher total taxes for prior years, Dorn said. He also is outside counsel to the Human Rights Campaign, which advocates for lesbian and gay Americans.

Spouses each making $100,000 or more a year probably will be subject to a marriage penalty because of how income-tax brackets are set for couples compared with singles. By comparison, where one person earned $175,000 and the other $25,000, they would probably see a benefit to filing jointly.