We have been separated but not legally for 4 years. Husband did not claim 2008 and 2009 taxes until recently and I thought he had. (Dumb me) He finally had them done by a tax attorney and he's claiming HOH for both 8 and 9 and then will again for 2010. The tax attorney did my taxes for 8 and 9 and I'm getting a refund but he put my status as single since husband is claiming HOH and single . If husband files HOH do I still have to file married filing separately? My refund is not substantial and I don't think the change in status will make a big difference in refund but is it legal for me to file as single? I feel like I should stay consistant with 2010 which I'm doing myself, but is filing single in my cirucumstance legal?

“ If husband files HOH do I still have to file married filing separately?”----> Yes you can; as you are STILL married(because you have been separated but not legally), then you can file separate tax returns. The married filing separately (MFS) filing status is the least beneficial of all the filing statuses.
“but is it legal for me to file as single? I feel like I should stay consistant with 2010 which I'm doing myself, but is filing single in my cirucumstance legal?”----> No; you can’t file your return as single; you are still married. If you were legally separated under a separate maintenance order issued by a court, then you can file your return as single.