@Opus 17 - it is only a requirement that a Qualifying Relative (normally a child) LIVES with you ; there is no requirement that the taxpayer CLAIM a qualifying relative to obtain HOH filing status.
https://www.irs.gov/pub/irs-pdf/p501.pdf
page 8 left side: A qualifying person lived with you in the home for more than half the year
So two unmarried parents living together and the child lived with them for more than 6 months: Parent A provides more than 50% of the household expenses files HOH and Parent B files SINGLE. Those filing status' do not change even if Parent B claims the child.
Can you provide the IRS pubication that supports this rule:
<<This rule is not available for two parents living together unmarried and sharing custody.>>
