Specifically, under a feature of California law that recognizes domestic partnerships gay couples must now combine their income and report half of it on each of their respective returns.
The ruling marks the first time that the IRS has recognized same-sex couples as equal to their heterosexual counterparts for tax purposes. Of the community-property states (i.e. all property and debt is owned equally by a couple) Nevada and Washington also recognize domestic partnerships, so couples there may also be affected.

The head of the IRS said Thursday that a government shutdown during tax season would be a challenge the agency has never confronted before — and one that would become more complicated as the April filing deadline draws closer. Doug Shulman, the IRS commissioner, also signaled at a House Ways and Means subcommittee hearing that his agency was discussing how to address a potential shutdown with the Obama administration, though he did not spell out any details of those talks. “We run a $13 billion financial services operation, so the idea of stopping it for a few days or a few weeks is strange,” Shulman said, adding that he was hopeful, based on ongoing negotiations, that a shutdown could be averted. [