@NCperson
No. Look at table 4, "who is a qualifying person".
The first row shows the case where the qualifying person is a qualifying child who lived with you more than half the year. "Qualifying child" is defined in the dependent section, and is a dependent who meets certain tests. That's where we get dragged into what happens if a child qualifies to be claimed by more than one person, and the tiebreaker rules that apply if a child is claimed by more than one person.
The bottom line is that in this case, with two unmarried parents living together with their child, the child can only be a qualifying person for HOH for taxpayer A if the child is also a qualifying child dependent for taxpayer A. If A doesn't claim the child dependent, the child is not a qualifying person for HOH. Turbotax will not transmit a tax return for HOH unless the child is listed as a dependent. If taxpayer A wants to use the child as a qualifying person for HOH, while taxpayer B wants to use the child to qualify for the child tax credit and EIC, this will be rejected. (And turbotax will only allow the attempt if the taxpayers invoke the special rules for parents who live apart and share custody.) If it goes through on paper, the IRS will send investigation letters to both taxpayers. This has happened dozens of times in this forum, usually because unmarried parents who live together and share custody misunderstand the custody questions in the dependent interview.
It just won't go through the system the way you want it to. This is 15 years experience talking. A child can only be a qualifying person for HOH if (a) they are first a qualifying child dependent, or (b) the taxpayers invoke the special rules for children of divorced or separated parents.
