Publication 972: https://www.irs.gov/publications/p972 (Check here for updated information)

IRS Interactive Tax Assistant: https://www.irs.gov/help/ita/does-my-childdependent-qualify-for-the-child-tax-credit-or-the-credit-for-other-dependents

To qualify for the Child Tax Credit, one must have a Qualifying Child

A qualifying child for purposes of the Child Tax Credit is a child who:

1. Is your son, daughter, step-child, foster child, brother, sister, step-brother, step-sister, half-brother, half-sister, or a descendant of any of them (ie., your grandchild, niece, or nephew),

2. Was under age 17 at the end of current tax year,

3. Did not provide over half of his or her own support for the tax year,

4. Lived with you for more than half of the tax year,

5. Is claimed as a dependent on your return,

6. Does not file a joint return for the year (or files it only to claim a refund of withheld income tax or estimated tax paid), and

7. Was a U.S. citizen, a U.S. national, or a U.S. resident alien. For more information, see Publication 519, U.S.Tax Guide for Aliens, if the child was adopted.

Limits on the Credit

It is a must to reduce the Child Tax Credit if either (1) or (2) applies.

1. The amount on Form 1040, line 47; Form 1040A, line 30; or Form 1040NR, line 45, is less than the credit. If this amount is zero, you cannot take this credit because there is no tax to reduce.

2. Your modified Adjusted Gross Income (AGI) is more than the amount shown below for your filing status.

   a. Married filing jointly—$400,000.

   b. All other filing statuses—$200,000

   The taxpayer may be able to take the Additional Child Tax Credit.