Two different things. Either the IRS denies the claim of the parent that did not submit a signed 8332 form and send them a letter request that form or they just pay the claim without the form. The parent that did not live with the child cannot file an electronic tax return without either claiming to have an agreement signed by you and attaching it to the tax return (or mail it if the return is e-filed), or saying the child lived with them.
If two taxpayers claim the same child, and the IRS pays the claims, then in a year of so the IRS will send letters to both taxpayers asking them to supply information to support their claim that the child physically lived with them the required length of time.
At that point they are not interested in any agreement or 8332 form because they have already the claim, they just want to establish which taxpayer the child physically lived with.
The supporting information is school records, medical records, any other documentation with the child's name and address, statements from neighbors, etc, that would establish which parent the child physically lived with.
The IRS will evaluate each claim and award the claim to one taxpayer, the other will have to pay back any refund plus interest and possible penalties.
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
