If there are two qualifying children, each parent may claim the credit on the basis of one of the children.

One parent may claim the credit on the basis of both children.

If both parents claim the child as a qualifying child, the IRS will treat the child as the qualifying child of the parent with whom the child lives for the longer period of time in the tax year. If the child lives with each parent for the same amount of time, the IRS will treat the child as the qualifying child of the parent who has the higher adjusted gross income (AGI) for the tax year. 

If no parent can claim the child as a qualifying child, the child is treated as the qualifying child of the person who has the highest AGI for the tax year.

If a parent can claim the child as a qualifying child but no parent does so claim the child, the child is treated as the qualifying child of the person who has the highest AGI, but only if that person's AGI is higher than the AGI of any of the child's parents.

 If you do not meet all of them, you must use Form 1040A (PDF) or Form 1040 (PDF).