In most situations, you can only claim a child as a dependent if they lived with you for over 50% of the tax year. It’s standard that the taxpayer with whom the child lives with, in most cases the custodial parent, has the right to claim the child and the associated credits and exemptions.
There is a way that non-custodial parents can claim the child, however. If the parent who has legal custody of the child fills out a
Form 8332, Release of Claim to Exemption, then the other parent of the child is entitled to claim him/her as a dependent. This form releases the right to claim the child as a dependent for purposes of an exemption. Usually, this is the only way you can claim a child who didn’t live with you as a dependent, typically because they qualify to be claimed by another taxpayer.
The parent that the child lives with for the larger part of the year is considered the custodial parent. The child’s other parent is referred to as the noncustodial parent.
During the tax year, if the child’s parents separated or divorced, the parent with whom the child lives for the most part of the year post-separation is considered the custodial parent.