The child tax credit is worth up to $1,000 for each qualifying child, as of 2015, reports About.com. The amount phases down gradually once a taxpayer's income reaches a maximum level. If child tax credits reduce federal tax liability to zero, the taxpayer may be able to obtain a refund for the extra credits.
The Internal Revenue Service subtracts $50 from the maximum $1,000 child tax credit for every $1,000 of income over the maximum of $75,000 for singles, $55,000 for married couples filing separately and $110,000 for married couples filing together, explains About.com. A taxpayer can claim any amount of children for tax credit purposes as long as they are eligible.
Children qualifying for the child tax credit can be sons, daughters, stepchildren or foster children, states the IRS. They can also be siblings, step-siblings or their descendants. They must be age 16 or under at the end of the tax year, claimed as a dependent on the taxpayer's return and dependent on the taxpayer for more than half their support. Additionally, they must have lived with the taxpayer for over half the year and be U.S. citizens or resident aliens. To assist taxpayers in finding out if they qualify for the credit, the IRS has a tool on its website called Am I Eligible for the Child Tax Credit.