Marital law, however, requires no such documentation, and such laws would apply for couples married in Massachusetts or Canada, or registered in Vermont, New Hampshire, Connecticut, New Jersey, Washington, California and Oregon. There are presumptions about shared assets that are imposed on couples without regard to title, Hertz says.

In California, for instance, if the source of the money is income earned after the two parties were registered, it is considered to be owned 50/50, regardless of whose name the bank account is in. The rules vary slightly from state to state, but in general, there's a presumption of sharing, a presumption of duty, and if you don't like it, you have to opt out of it-with a pre-nuptial arrangement.

The old way, there was a presumption of separateness, of individuality, and if you wanted to share, you had to opt in to sharing. The new way is where marital laws apply and there's a presumption that the assets are shared, and if you don't like it, you have to opt out-with a pre-nuptial arrangement," Hertz says. "There's been a complete reversal of the default rules."

The truth is, with the federal government not recognizing same sex unions, gay marriage-from a strictly financial perspective-is a pretty bad deal, according to planners. It may be why most of the planners interviewed says only about half of their gay clients have decided to marry. In marriage, gay couples are lumbered with many of the obligations of a marriage while receiving few of the benefits.

Only in New Jersey is it more financially beneficial for a gay couple to marry rather than remain single. And that's because of the state's inheritance tax, which can be punitive, according to Jennifer Hatch, president of Christopher Street Financial, an investment advisory firm that serves the gay and lesbian community. In New Jersey, if anyone leaves anything to a non-linear family member-say a cousin, a neighbor or a gay partner-there is an inheritance tax of as much as 17%, almost from dollar one, Hatch says.

"You can leave someone $50,000, and you'll get hit with this," Hatch says. "For gay couples, if they have a civil union, they become next of kin and they don't have to pay this tax."

And while federal tax laws are generally more advantageous for heterosexual married couples than for those of the same sex, there's one benefit to being married and gay, and it stems from the fact that the IRS doesn't recognize gay marriage: The partners continue to file taxes as individuals. That means all of the caps afforded to individuals are retained, says Dana Levit, a CFP licensee in Newton, Mass., and president of PridePlanners Association, a nonprofit group that educates financial professionals on the needs of nontraditional families.

For instance, where married couples must combine their income when figuring out how much mortgage interest they can deduct-the interest deduction erodes for income above $150,000-gay couples filing as individuals will take longer to bump up against that threshold.

That's no small matter. Deducting mortgage interest is one of the largest deductions most people can take. For someone who earns $50,000 a year and falls into the 30% tax bracket, for instance, a $5,000 mortgage interest deduction could save them $1,500 in taxes.

"This is where it's a good thing to be gay," Levit says. "Things that get phased out for joint filers just don't apply."