Here (in Massachusetts):

the first state to legalize gay marriage, couples have had to fill out MULTIPLE tax returns.
First, federal tax return as married (one if filing together, two if married filing separately, three if you need to compare)
Second, do the state return using the married numbers from above
Third, do the ‘real’ federal tax returns as two single people because they were not allowed to file as married

People joke about the privilege of paying taxes together, but seriously it was a huge and expensive pain for married gay couples to file up until now.

On the plus side, in the first five years, legalized gay marriage brought Massachusetts an estimated $111 million in increased tourist revenue. Big boom for the local wedding industries.