Do I need to file an amendment?I've been filing taxes as a single for the past four 4. When I started filing taxes I was married but separated due to family violence.

[xmasbaby0]

If you are still legally married your filing choices are to file a joint return or married filing separately.  Filing as "Single" is not an option---and if you have been doing that, your tax returns have been prepared incorrectly.  There are a a few states in which a legal separation would allow you to file as "single."  Do you have any sort of legal documents to show legal separation?  

Or----are there children that are living with you?   If so, you could be filing as Head of Household.   Please provide some details without any personal information.