You can’t find out who claimed your child on taxes. The IRS knows exactly which return used your child’s Social Security number, but federal law prohibits the agency from telling you the other filer’s identity, even when you’re clearly the one entitled to the claim. What you can do is file your own return claiming the child, force the IRS to investigate both returns, and prepare the documents that prove the child is your dependent. The tie-breaker rules then decide who keeps the claim.
Why the IRS Won’t Name the Other Filer
Under IRC ยง 6103, tax returns and return information are confidential. IRS employees cannot share them with you except in narrow situations, and a dependent dispute between two filers is not one of them.1Office of the Law Revision Counsel. 26 US Code 6103 – Confidentiality and Disclosure of Returns and Return Information
The IRS has stated this directly for dependent identity theft cases: the agency “is prohibited from telling you who claimed your dependent(s)” because privacy law only permits disclosure when the victim’s name and SSN appear as the primary or secondary taxpayer on the other return, not merely as a dependent listed on it.2Internal Revenue Service. Identity Theft Dependents
That rule doesn’t bend for court orders you show the IRS, for police reports, or for calls to the taxpayer advocate. The name stays sealed.
How You Usually Find Out
Two things typically tip people off. The first is an e-file rejection. When you submit your return and the child’s SSN already appears on an accepted return for the same tax year, your software returns an error, usually flagging a duplicate SSN for a dependent.
The second is Notice CP87A in the mail. This notice is specific to dependent conflicts. It tells you another taxpayer claimed a dependent with the same SSN that appears on your return, and it lists the last four digits so you can confirm which child it involves. It does not identify the other filer or give you any lawful way to find out.3Internal Revenue Service. Understanding Your CP87A Notice
Who It Usually Is
Even without the IRS confirming anything, most people have a strong sense of who filed the competing claim. It is almost always someone in the child’s life: an ex-spouse, a co-parent, a grandparent the child spent time with, another relative who helped with expenses. If that list feels obvious in your situation, treat this as a dependent dispute and focus on proving your claim. If none of it fits and the conflict genuinely came out of nowhere, treat it as possible identity theft instead (covered below).
Confirm You Actually Qualify to Claim the Child
Before you fight the claim, run through the five tests the IRS uses for a qualifying child. All five must be met:
- Relationship. Your son, daughter, stepchild, foster child, sibling, or a descendant of any of these (a grandchild or niece, for example).
- 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 for more than half the year, with exceptions for temporary absences like school, medical care, or military service.
- Support. Did not provide more than half of their own support for the year.
- Joint return. Did not file a joint return, unless the return was filed only to claim a refund of withheld taxes.
Fail one test and you don’t have a valid claim, no matter what the other filer did.
Tie-Breaker Rules When Two People Both Qualify
Sometimes two people both legitimately pass all five tests. Divorced parents sharing time, or a parent and grandparent in the same household, can each meet the qualifying child rules for the same child. The IRS resolves these automatically with a hierarchy:
- A parent beats a non-parent.
- Between two parents who don’t file jointly, the parent the child lived with longer during the year wins.
- If residency was equal, the parent with the higher adjusted gross income wins.
- A non-parent can claim the child only if no parent claims them, and only when the non-parent’s AGI is higher than the AGI of any parent who could have claimed the child.
- Among non-parents only, the person with the highest AGI wins.
You don’t elect these rules; the IRS applies them once it examines both returns.
Divorced or Separated Parents
A custody agreement or divorce decree that says who claims the child in which year does not, by itself, settle anything with the IRS. For any decree or separation agreement executed after 2008, the IRS requires Form 8332 signed by the custodial parent to let the noncustodial parent claim the child. A copy of the decree is not a substitute.6Internal Revenue Service. Divorced and Separated Parents
Form 8332 transfers only certain benefits: the Child Tax Credit, the Additional Child Tax Credit, and the Credit for Other Dependents. It does not transfer the Earned Income Tax Credit or head of household filing status, which stay with the custodial parent regardless of what any decree says.7IRS.gov. Form 8332 Release/Revocation of Release of Claim to Exemption for Child by Custodial Parent
A custodial parent who signed Form 8332 can revoke it using Part III of the same form. The revocation takes effect the following tax year and requires giving the noncustodial parent a copy.
What to Do When Your Return Is Rejected
If e-file rejects your return for a duplicate dependent SSN, you have two paths. If you have a current-year Identity Protection PIN as the primary filer, you can resubmit electronically with the PIN included. Otherwise, file the return on paper.8Internal Revenue Service. Age, Name or SSN Rejects, Errors, Correction Procedures
On the paper return, write “Rejected Electronic Return” in red at the top of the first page along with the rejection date, and include a copy of the rejection notification. Don’t attach documentation to prove the dependent claim yet; the IRS will ask for it later if needed. To stay timely, the paper return must be postmarked by the later of the original due date (with extensions) or 10 calendar days after the rejection notice.8Internal Revenue Service. Age, Name or SSN Rejects, Errors, Correction Procedures
Filing on paper is what triggers the IRS to look at both returns. Once your return is in the system claiming the same child as the earlier one, the agency sends CP87A to both filers and begins examining who actually qualifies.
What to Do If You Received Notice CP87A
CP87A means the IRS already sees two returns claiming the same child and is asking you to review the qualifying child rules. If you’re entitled to the claim, you don’t have to respond immediately. The IRS will contact the other filer with the same notice and investigate.3Internal Revenue Service. Understanding Your CP87A Notice
If, on review, you realize you shouldn’t have claimed the child, file Form 1040-X to amend and remove the dependent. Correcting the return yourself is far better than waiting for the IRS to disallow the claim.9Internal Revenue Service. File an Amended Return
Documents That Prove the Child Is Yours to Claim
If the dispute moves to examination, the IRS asks for supporting documents using Form 886-H-DEP. Records that carry weight include school, medical, daycare, and social service records showing the child’s name and your shared address. Letters on official letterhead from schools, medical providers, social service agencies, or places of worship confirming names, a common address, and dates also work. Documents signed by a relative do not count.10Internal Revenue Service. Form 886-H-DEP Supporting Documents for Dependents
The people who lose these disputes are almost always the ones who can’t produce paperwork showing the child actually lived with them. Gather what you have before the IRS asks.
If You Suspect Identity Theft Instead
When no relative, co-parent, or caregiver could plausibly have claimed your child, treat the situation as possible identity theft. File Form 14039, the Identity Theft Affidavit, checking the box indicating you’re submitting it for 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 flag your child’s account for added protection. Identity theft cases resolve more slowly than ordinary dependent disputes, so expect delays on any refund. Once resolved, request an IP PIN for the child to prevent a repeat.2Internal Revenue Service. Identity Theft Dependents
How to Keep It From Happening Again
Get an IP PIN for Your Child
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, and any attempt to do so is rejected automatically. The program is voluntary but strongly encouraged.12Internal Revenue Service. Frequently Asked Questions About the Identity Protection Personal Identification Number (IP PIN)
Request one through the IRS “Get an IP PIN” online tool after identity verification. For a dependent who doesn’t have their own IRS account, you may need to apply by mail with Form 15227 or in person at a Taxpayer Assistance Center with identification documents.
Sort It Out With the Co-Parent Before Filing
The most preventable version of this problem is two co-parents both claiming the same child because neither checked with the other. Confirm the arrangement before filing season, even if your custody order already specifies alternating years. A brief conversation costs nothing; an IRS examination costs months.
Keep Residency Records as They Come In
Don’t reconstruct a year of records after the notice arrives. Save school enrollment paperwork, medical visit summaries, and daycare documentation as they’re generated. A folder built over twelve months is far more convincing than one assembled under deadline.
File Early
Filing promptly once your documents are ready reduces the odds that someone else’s return gets accepted first. It doesn’t stop the IRS from investigating a later duplicate, but it does mean your return processes first and the other filer is the one facing a rejection.