@ediben11 - depends on the state and the rules for that state. Can't comment without knowing the two states in question.
Also, while you stated you will thus file "joint" on federal, if there is no agreement for both to sign the tax return, then it has to be 'Married- Filing Separate". And based on your last comment, engaging a lawyer before you agree to file in April may be an approach to consider.
Also, while all the commentary has focused on the "6 month rule", if there is a signed legal separation agreement in place that is 'good enough' for the IRS to prove separation, even if the legal separation agreement is signed on Dec. 31. Then filing HOH (assuming the child lived with you for 183 days or more) becomes a much "easier putt".
