How do you claim a child if you agree with your ex-spouse to claim him 6 months and he claims him the other 6 months of the year?

The dependency exemption can not be split. Generally, the custodial parent is treated as the parent who provided more than half of the child's support. This parent is usually allowed to claim the exemption for the child if the other exemption tests are met. However, the noncustodial parent may be treated as the parent who provided more than half of the child's support if certain conditions are met.

The custodial parent signs a Form 8332 (PDF), Release of Claim to Exemption for Child of Divorced or Separated Parents, or a substantially similar statement, and provides it to the noncustodial parent who attaches it to his or her return. Please beware that if the custodial parent releases the exception, the custodial parent may not claim the Child Tax Credit.