Im still legally married but have been informally seperated scince 4/1/17 should i file single or married filing seperate

[maglib]

your state will determine your status. Many states require divoce to be finalized to be considered single or possibly head of household. <a rel="nofollow" target="_blank" href="https://turbotax.intuit.com/tax-tips/marriage/tax-tips-for-separated-couples/L6H4vr1nd">https://turb...>

[tbryant]

I live in ny

[Opus 17]

Even legal separation in NYS does not count as "unmarried."  I looked up the tax court cases on this a few years ago while I was separated.

[Opus 17]

You can't file as single unless you are considered "unmarried" according to state law.  In some states, even a legal separation is not enough to be considered unmarried, and I doubt that an informal separation allows you to be considered unmarried in your state, but that would be a question for an attorney.

If you are not "unmarried" then you file married filing jointly (if you and your spouse agree), or married filing separately, or head of household (if you paid more than half the costs of keeping up your home, and provided care in that home for a qualifying person who is usually a child dependent, and you were separated all of the last 6 months of the year.)

[maglib]

The only exceptions to this rule apply to married individuals

one spouse is a New York State resident and the other is a nonresident or part-year resident. In this case you must either:
file separate New York State returns using filing status 3; or
file jointly, as if you both were New York State residents, using filing status 2.
 
you are unable to file a joint New York return because the address or whereabouts of your spouse is unknown, you can demonstrate that reasonable efforts have been made to locate your spouse, and good cause exists for the failure to file a joint New York return. In this case, you may file a separate New York return using filing status 3.
 
your spouse refuses to sign a joint New York return, reasonable efforts have been made to have your spouse sign a joint return, there exists objective evidence of alienation from your spouse such as a judicial order of protection, legal separation under a decree of divorce or separate maintenance, or living apart for the twelve months immediately preceding application to file a separate return or commencement of an action for divorce or commencement of certain court proceedings, and good cause exists for the failure to file a joint New York return. In this case, you may file a separate New York return using filing status 3.