Interesting article in today’s Washington Post, Claiming "Head of Household" Just Got Harder, by Albert B. Crenshaw:

When it comes to income taxes, a "dependent child" is a dependent child, yes? Well, yes, since 2004, when Congress more or less unified the five different definitions of the term. So now the one definition applies when calculating head-of-household filing status, the exemption for a dependent, the child tax credit, the child and dependent care credit and the earned-income tax credit.

But the new definition in some ways tightens up the rules, particularly concerning head-of-household status, and not everyone will benefit. Already, tax preparers working with low- and moderate-income families and the elderly are finding that some of their clients who could file as heads of households in the past will not be able to do so on their 2005 returns.