I have a divorced couple that agreed to alternate the children each year for tax purposes. This is the first year the dad puts them but the children live with the mother. If I put the taxpayer as Head of Houesehold on the return and mark on dependent list that each child is N- Dependent child who did not live with client due to divorce or separation I get an error that states "Federal Information Worksheet: Head of Household's child must be entered OR you must enter the information for the qualifying dependent in the Dependent Section" and the boxes for the quaifying person's name and SSN under the HOH filing status are marked in red.
The definition of HoH is codified under §2(b) with reference to §152(c) for the definition of qualifying child.
Your client is not otherwise able to claim those as qualifying children under §152(c) but for §152(e), which deals with children of divorced parents. For purposes of HoH, however, §2(b)(1)(A)(i) specifically stipulates that §152(e) is to be disregarded.
That's why your client can't claim HoH in spite of the release.