Inability to file taxes jointly results in major differences in tax liability. Consider a gay couple where one partner has a taxable income of $40,000 and the other a taxable income of $20,000. If the couple could file their federal taxes jointly, the tax bill would be $8,217.50 but filing separately they must pay $9,032.50, an additional expense of 815 dollars.

In addition to the potential expense of filing separately, gay couples must pay income taxes on benefits paid to spouses such as health benefits. That additional taxable income can increase the tax rate that the individual must pay and can add up to thousands of dollars in extra taxes not paid by their heterosexual counterparts.

Gay couples who own a home together must also decide how much of the mortgage interest payments each partner will use as a deduction, and couples with children must decide which partner gets to claim them as dependents for tax purposes on federal returns and returns in states that don’t recognize same-sex unions.