“You may have some good for some couples but also some bad lurking out there,” said Levitan of Holland & Knight.

Advisers including Levitan want the IRS to clarify what happens when couples reside and own a home in a state such as Massachusetts, which recognizes gay marriages, as well as a vacation property in Florida, which doesn’t.

State Differences

“Do we have to treat that property differently for marital deduction purposes because it’s subject to Florida law?” she said.

States will wait to make changes until they see the IRS guidance, said Verenda Smith, deputy director at the Federation of Tax Administrators.

The decision won’t affect the way same-sex couples in California are required to file their state-tax returns because the state generally affords the same rights to those individuals as other spouses, Daniel Tahara, a spokesman for the state’s Franchise Tax Board, said in an e-mail.

Arizona’s Rules

In Arizona, which doesn’t recognize same-sex marriages, the state-tax filing process also won’t change, said Sean Laux, a spokesman for the Arizona Department of Revenue. Married-filing- jointly or married-filing-separately returns wouldn’t be allowed for same-sex couples, Laux said. Those who are non-residents with earnings in Arizona would file as single people to report income apportioned to the state, he said.

“We’re waiting to see what the feds decide on how to treat where the married couple lives or where they got married,” Laux said. “That will impact the things we and other states have to deal with.”

The most significant savings for gay married couples generally will come from the ability to now use the unlimited marital deduction for federal estate-and-gift tax purposes, said Geoff Seaman, a strategist for the Bank of New York Mellon Corp.’s wealth management unit.