If unmarried parents are living together with their child for the entire year, and both parents are contributing to the cost of maintaining the household for the child and themselves, may they both file as head of household?

Only one parent in the household can file as head of household. A taxpayer filing as head of household must furnish more than half the cost of maintaining the household. The child is the qualifying child of each parent. The parent who provided more than half of the cost of maintaining that household may file as head of household. The other parent would have to file as single.