The options are:
Married filing jointly. You can always file jointly if you both agree, and you may owe less tax that way, but there are other complications.
Married filing separately. This is how you will file if you don't qualify for single or head of household (below).
Head of household. You can file as HOH if you have been separated for at least the last half of the year (since July 1, 2024) and you provide care in your home for at least one qualifying dependent, usually your child.
Single. The IRS says you can file single if you are "considered unmarried" because you are "Legally separated from your spouse under a divorce or separate maintenance decree." (And, "State law governs whether you are married or legally separated under a divorce or separate maintenance decree.")
I bring this up because it is in the rules, but no one actually qualifies. I have found several court cases where this was not allowed, and have not found a court case where it was allowed. The type of legal separation that might qualify went out of style in the 1950s or 1960s. The courts have ruled that it must be a final separation that can't legally be reversed (legally barred from reconciling even if you wanted to), and the support order has to be final (a temporary order during separation that will be finalized when the divorce is finalized doesn't count.). If you think you might qualify in your situation, see a local attorney for advice.
