The IRS does not get involved in determining if custody conditions are being followed or if terms of divorce decrees are being fulfilled. Local courts do not have jurisdiction over the IRS.
Just as each court has its administrative procedures and forms, the IRS also has its own administrative procedures and forms based in US law.
The IRS recognizes the custodial parent as having the higher legal claim to a dependent unless they waive it in writing with Form 8332.
The Family Court attorneys have the responsibility to include in divorce decrees the necessary language to align the tax law requirements with the Family law negotiations to allow for smooth sailing of child custody and tax filing matters.
Sometimes this process works easily, and sometimes taxpayers end up back in Family Court as they encounter the reality of the disconnects between their decree stipulations and the actuality of the tax law.
From an IRS perspective, the noncustodial parent needs to have the signed Form 8332 attached to their tax return to back up their claim for any dependent that does not reside with them more than half the year.
