Legal separation is granted by the court with a court order that can either be decree of divorce or a separate maintenance decree. And you can find more on that here IRS Pub 17 - Filing Status
If your court/state law considers you "unmarried" you are allowed to file Head of Household or Single. There are some states that do not recognize legal separations. The information below explains your filing options if you are legally separated.
And if you are eligible to claim Head of Household, you must meet all 5 conditions listed here https://ttlc.intuit.com/questions/2567672
NOTE: If you are having doubts as to your status in your state, I recommend to check with a local attorney who specializes in family law or the one that handled your separation.
- If tax law considers you "unmarried" because you got a decree of separation maintenance prior to December 31, you can file with "single" or "head of household" status.
- The IRS considers you married for the entire tax year when you have no separation maintenance decree by the final day of the year. If you are married by IRS standards, you can only choose "married filing jointly" or "married filing separately" status. You cannot file as "single" or "head of household."
- "Head of household" requires you to have a dependent and pay at least half of the expenses needed to maintain a home. If your dependent is a child who lives with you more than with your spouse, the IRS considers you to be the custodial parent.
- Your deductions and credits as custodial parent depend on whether your spouse has agreed to waive his ability to claim the child as an exemption under Box 6a on the 1040 form -- only one of you can claim the child as an exemption. When you can claim the dependency exemption, you can claim child-related credits.
