Publication 17
taxmap/pub17/p17-173.htm#en_us_publink1000174546To claim the child tax credit, you must file Form 1040 or Form
1040A. You cannot claim the child tax credit on Form 1040EZ. You must provide
the name and identification number (usually a social security number) on your
tax return for each qualifying child.
If you are filing Form 1040, answer the
Questions
in your form instructions for line 51, Form 1040, to find out which child tax
credit worksheet you can use to figure the credit.
If you answer "Yes" to question 1 or 2 in your Form 1040 instructions,
you must complete the child tax credit worksheet in Publication 972. Otherwise,
you can use the Child Tax Credit Worksheet in your Form 1040 or Form 1040A
instructions. (See
Example, later.)