I have been filing single during the past 4 years I have been married because my husband is a United Nations employee and a foreigner who doesn't pay any taxes. He doesn't have a S.S. # or tax payer ID and doesn't want one. I had asked my cousin's husband who is an accountant when I got married how I should file and he told me to file single. So that's what I've been doing. I've had my taxes done by 2 different accountants (the last one has done my return for the past 3 years) and this year he says to me-" by the way- you know you're supposed to be filing married filing separately, right?". Which totally freaked me out because now he's saying I've been doing something illegal for the past 4 years and noone had pointed this out before. Now I need to know am I doing something illegal? I have 2 kids now and I think I will end up owing many thousands of dollars (which I don't exactly have sitting around), if I file amended returns for the past 4 years. Can someone please clear this up for me once and for all? Should I open this can of worms and call the IRS and try to amend it or should I just continue filing single?