Head of household rules: (note: TurboTax will walk you through this also)

Things I found on the IRS website:

Filing Status  https://www.irs.gov/help-resources/tools-faqs/faqs-for-individuals/frequently-asked-tax-questions-an...
Question: I am divorced with one child. This year my ex-spouse, who is the noncustodial parent, will claim an exemption for our child. Do I still qualify as head of household?
Answer:

You may still qualify for head of household filing status even though you aren't claiming an exemption for your child, if you meet all of the following requirements:

    You're unmarried or considered unmarried on the last day of the year.
    You paid more than half of the cost of maintaining a household that is your home and the main home of your child for more than one-half of the year.
    Your child is either your qualifying child (whether you can claim the child as a dependent or not) or your qualifying relative whom you can claim as a dependent.

 Question: To qualify for head of household filing status, do I have to claim my child as a dependent?
Answer:  https://www.irs.gov/help-resources/tools-faqs/faqs-for-individuals/frequently-asked-tax-questions-an...

Generally, to qualify for head of household, you must have a qualifying child or dependent. However, a custodial  parent may be able to claim head of household filing status with a qualifying child even if he or she released a claim to exemption for the child. See Noncustodial parent is claiming an exemption for my child; do I still qualify as head of household?