How to sort through the changes for same-sex tax filers

Married same-sex couples this year will file their U.S. income tax returns just like heterosexual married couples because of the Supreme Court's decision in June to strike down key parts of the Defense of Marriage Act.

For insight into how gay and lesbian couples should plan this tax season, we turned to Nanette Lee Miller and Janis Cowhey McDonagh, who head accounting firmMarcum's LGBT and nontraditional family practice.

Marcum started its LGBT practice in 2012, and it has grown rapidly as same-sex couples struggled to deal with the patchwork of financial rules.

"A lot of LGBT couples want the specialty we have, but some just want to walk into a friendly environment," McDonagh says. "I had a client who came in, and said: 'My last accountant didn't like me and didn't approve of me getting married.'"

Here is what McDonagh, who is based in New York, and Miller, who is in San Francisco, say will be different this year:

Q: Will married same-sex taxpayers, who previously were forced by the Defense of Marriage Act to file as single or heads of household on their federal returns, see their taxes go up or down this year? And under what circumstances?

Miller: If one has a salary and the other doesn't, they may save money. Otherwise, they will pay a little more. Equality means that they can all complain on the same issue.

McDonagh: The majority of my clients are two high-wage-earners, and they are paying a lot more to file joint rather than single (because they now are in a higher tax bracket).

Q: Will tax season at least be a little easier this time?

McDonagh: In some respects, it is easier. You don't have to decide who is the head of household and who is going to claim the child. Before, I had to ask who owns the house and who is paying the mortgage taxes. Sometimes one party owned the home and the other one was making the mortgage payments off of income, so no one could take the deduction.

We have a big client who filed joint for the first time this year. One had been married years ago and had capital losses for tax purposes from when he was divorced. He'd never generated the gains to use against it, and the other one was able to sell and generate some gains. As soon as they could file a joint return, they got back $85,000.

Miller: You can put that under the category of pleasant unintended consequences. Unlike the unpleasant unintended consequences.

Q: While the federal rules are now clear, the state rules remain a patchwork. What issues come up at tax season for same-sex couples whose lives span states where their marriage is recognized, and others where it is not?

McDonagh: That's what we've been dealing with in New York for years. We filed taxes for couples single for federal purposes and married at the state level. Now that may flip.

It is inconvenient because most state returns are based off of federal returns, so you are duplicating your work. A lot of my clients get K-1s (for partnership or trust income) and income from several states, so we need to look at each state's law to see how to file.

There are a few states that do not recognize same-sex marriage but will allow you to file jointly. That's the case in Missouri and Colorado. Their state returns are based on federal returns; they just threw their hands in the air and gave up.

Q: Are there particular issues for same-sex couples with kids?

McDonagh: One thing that's come up was the adoption credits. Previously, when you were doing a second-parent adoption, you could take those credits. Now you cannot because you are married, and you cannot take them when you are adopting your spouse's child. So you are losing out on your adoption credit.

Also, I had some couples who took each other as a dependent on their tax returns; that goes away with a joint return.

Q: Married same-sex couples who were prohibited from filing joint tax returns can now go back and amend their previous year's returns for the past three years if they were married then. Should they?

Miller: We have not had that many people go back and file revised returns. I was surprised that not that many people went back.

McDonagh: It's expensive to go back and amend a return. We had one that was worth going back and amending for 2010 because one (of the people) was in school. They amended 2010 and not 2011 or 2012. You can take it year by year.

Q: Is doing the returns now easier and less costly?

Miller: If you are married, it should be easier. In California, where you had to do allocated returns (because of the state's community property rules), it probably added 33 percent to the fee because you had to do all these dummy returns.

McDonagh: It's definitely a third to a half less now. It is nice to tell people that their costs are going down this year.

(The opinions expressed here are those of the author, a columnist for Reuters.)

(Editing by Beth Pinsker and Lisa Von Ahn)