Final answer:
Form 8332 is the document required when a custodial parent releases their claim to a child as a dependent for the noncustodial parent.
Step-by-step explanation:
When a custodial parent releases their right to claim a child as a dependent to the noncustodial parent, the required form is Form 8332: Release/Revocation of Release of Claim to Exemption for Child by Custodial Parent. This IRS form allows the noncustodial parent to claim the child as a dependent for tax purposes, provided that the custodial parent signs the form, and the other tax requirements are met.