You cannot find out who claimed your child on taxes. The IRS knows exactly who filed the competing return, but federal privacy law bars the agency from telling you, even when the other claim is clearly wrong and even when you are the child’s parent. What you can do is file your own return claiming the child, which forces the IRS to investigate both returns and apply its tie-breaker rules to decide who keeps the dependent. In most cases the other filer turns out to be someone you already suspect: an ex-spouse, a co-parent, a grandparent, or another relative.
How You Learn It Happened
Two things typically tip people off. The first is an e-file rejection. When you try to submit your return electronically and your child’s Social Security number is already on an accepted return for the same year, the IRS blocks yours. Your tax software will flag a duplicate SSN for a dependent.
The second is a letter. Notice CP87A is the one tied to dependent disputes. It tells you another taxpayer has claimed a dependent with the same SSN that appears on your return and shows the last four digits so you can identify which child is involved. It does not name the other filer and gives you no way to find out.1Internal Revenue Service. Understanding Your CP87A Notice
Why the IRS Won’t Tell You
Under IRC § 6103, tax returns and return information are confidential. IRS employees cannot disclose them except in narrow circumstances, and a dependent dispute between two filers is not one of them.2Office of the Law Revision Counsel. 26 US Code 6103 – Confidentiality and Disclosure of Returns and Return Information
The agency has stated this plainly. Even when you are the victim of dependent-related identity theft, the IRS “is prohibited from telling you who claimed your dependent(s)” because privacy law only permits disclosure of return information when the victim’s name and SSN appear as the primary or secondary taxpayer on the other return, not merely as a dependent.3Internal Revenue Service. Identity Theft Dependents
So pressing the IRS, calling repeatedly, or filing requests for records will not produce a name. The practical path is to assert your own claim and let the IRS adjudicate.
Make Sure You Actually Qualify First
Before you file paper and start a fight, confirm you’d win it. The IRS uses five tests for a qualifying child, and all five must be met:
- Relationship: your son, daughter, stepchild, foster child, sibling, or a descendant of any of these.
- Age: under 19 at year’s end, under 24 if a full-time student, or any age if permanently and totally disabled. The child must also be younger than you or your spouse.
- Residency: lived with you more than half the year, with exceptions for temporary absences like school, medical care, or military service.
- Support: the child did not provide more than half of their own support.
- Joint return: the child did not file a joint return, unless only to claim a refund of withheld taxes.
Tie-Breaker Rules When Two People Both Qualify
Two filers can legitimately pass all five tests for the same child, which is common when a child splits time between divorced parents or lives in a multi-generation household. The IRS applies a fixed hierarchy:
- If only one claimant is the child’s parent, the parent wins.
- If both parents claim the child and don’t file jointly, the parent the child lived with longer during the year wins.
- If residency time is equal, the parent with the higher adjusted gross income wins.
- A non-parent can claim the child only when no parent claims them, and only if the non-parent’s AGI exceeds that of any parent who could have claimed the child.
- If no claimant is a parent, the highest AGI wins.
These apply automatically. You don’t elect them. When the IRS reviews both returns, this hierarchy settles the outcome.
Divorced or Separated Parents
A custody order that says you get to claim the child in a given year does not bind the IRS by itself. For any decree or separation agreement executed after 2008, the custodial parent must sign Form 8332 to release the claim to the noncustodial parent. A copy of the decree is not enough.6Internal Revenue Service. Divorced and Separated Parents
Form 8332 transfers only the Child Tax Credit, Additional Child Tax Credit, and credit for other dependents. The Earned Income Tax Credit and head of household status stay with the custodial parent (the one the child lived with for the greater part of the year) regardless of what any decree says.7IRS.gov. Form 8332 Release/Revocation of Release of Claim to Exemption for Child by Custodial Parent
A release can cover the current year, specified future years, or all future years, and it is revocable through Part III of the same form. A revocation does not take effect until the following tax year, and you must give the noncustodial parent a copy.
What to Do Right Now
If Your E-File Was Rejected
If you already have a current-year Identity Protection PIN as the primary filer, you can resubmit the e-filed return for the current tax year with the PIN included. Otherwise, or for prior years, you need to paper-file.8Internal Revenue Service. Age, Name or SSN Rejects, Errors, Correction Procedures
Write “Rejected Electronic Return” in red at the top of the first page along with the rejection date, and attach a copy of the rejection notification. Don’t bulk up the return with proof of your dependent claim at this stage. If the IRS wants supporting documents, it will ask by mail.
Your paper return must be postmarked by the later of the original due date (including extensions) or 10 calendar days after the IRS notified you of the rejection. That keeps the return timely.
If You Received Notice CP87A
CP87A means both your return and someone else’s claim the same child. Review the qualifying child rules. If you’re entitled to the claim, you don’t need to do anything immediately. The IRS sends the same notice to the other filer and investigates both returns.1Internal Revenue Service. Understanding Your CP87A Notice
If the review convinces you that you shouldn’t have claimed the child, file Form 1040-X to amend. Correcting voluntarily is far better than letting the IRS disallow the claim and add penalties.9Internal Revenue Service. File an Amended Return
What the IRS Will Ask For
If the dispute moves into examination, the IRS uses Form 886-H-DEP to request supporting documents. The evidence that carries weight: photocopies of school, medical, daycare, and social service records showing the child’s name and your shared address, plus letters on official letterhead from schools, medical providers, social service agencies, or places of worship confirming names, a common address, and dates. Documents signed by a relative do not count.10Internal Revenue Service. Form 886-H-DEP Supporting Documents for Dependents
The filer with the records usually wins. The filer without them usually loses, regardless of who was actually right.
If This Doesn’t Look Like a Family Dispute
If the competing claim came out of nowhere and no relative plausibly explains it, treat it as identity theft. File Form 14039 (Identity Theft Affidavit), check the box indicating you’re submitting it on behalf of a dependent child, and attach it to the back of your paper tax return.11Internal Revenue Service. Identity Theft Affidavit
The IRS still won’t tell you who filed the fraudulent return, but it will place a marker on your account. Identity theft cases resolve more slowly than ordinary dependent disputes, so expect refund delays. After the case is closed, request an IP PIN for your child to block a repeat.3Internal Revenue Service. Identity Theft Dependents
Preventing It Next Year
An Identity Protection PIN is a six-digit number the IRS assigns each year. Once your child has one, no return claiming that child can be e-filed without the correct PIN. Any attempt is rejected automatically.12Internal Revenue Service. Frequently Asked Questions About the Identity Protection Personal Identification Number (IP PIN)
You can request one through the IRS “Get an IP PIN” online tool after identity verification. For a dependent child without their own IRS account, you may need to apply by mail using Form 15227 or visit a Taxpayer Assistance Center with identification documents.
Beyond the PIN, two low-effort moves prevent most repeat conflicts. Confirm with any co-parent, before filing season, who is claiming the child this year, especially if a custody agreement alternates years. And file as early as you can once your documents are in hand. Filing early doesn’t stop the IRS from investigating a second return, but it means your return processes first and the other filer deals with the rejection.