96% of married couples file a joint return for all the reasons states earlier in this thread. It's almost NEVER beneficial to do it (other than for the 4% that have figured out to make it reasonable...and some of that 4% are simply spouses that refuse to sign the return so the other spouse is forced to file separately even though it's not advantageous)
if you think you are part of the 4%, set up your tax return and see what the refund is, then do it again as if you are EACH single and see what the result it. Highly likely "joint' is the way to go.
