Where to enter child's w2 income?

On the child's Form 1040, 1040A, or 1040EZ.

A separate tax return must be filed by the child (or for the child if the child is too young). A parent cannot report a child's W-2 income on the parent's tax return.

The only time a parent can report a child's income on the parent's return is if the kiddie tax applies and the child's only source of income is interest and dividends.