If someone else has already claimed your child as a dependent, the fix starts with filing your own return claiming the child, and then, if you know who the other filer is and believe they did it knowingly, reporting them to the IRS on Form 3949-A, Information Referral. That is the core of how to report someone claiming your child on their taxes. If a stranger used your child’s Social Security number, the right form is different, and the sections below walk through both paths, the evidence you will need, and what the IRS does after you file.
File Your Own Return First
Nothing happens until your return is in the system. A rejected e-file is not a filed return, so if your e-file bounces because your child’s SSN already appears on another return, you cannot stop there.
First, check that you typed the SSN correctly. Typos cause a surprising share of these rejections. If the number is right, you have two options. For the current tax year, you can still e-file if the primary taxpayer on the return has an Identity Protection PIN (IP PIN). For prior years, paper filing is the only route: print the completed return, sign it, and mail it to the service center listed in the form instructions. Do not attach documentation proving your right to claim the child. If the IRS needs records, it will ask for them by mail later.1Internal Revenue Service. Age, Name or SSN Rejects, Errors, Correction Procedures
Filing the return is what triggers the IRS dispute process. Once two returns claim the same child, the IRS has to sort out who qualifies.
Which Form to Use to Report the Other Person
Filing your return tells the IRS a conflict exists. It does not formally report anyone for wrongdoing. The right follow-up form depends on who the other filer is.
If you know or strongly suspect who claimed your child — an ex, a relative, a former roommate — and you believe they did it knowingly, file Form 3949-A, Information Referral. This form reports suspected tax fraud, including false exemptions, false deductions, and Earned Income Credit violations. You can complete and submit it directly on the IRS website.2Internal Revenue Service. About Form 3949-A – Information Referral
If a stranger used your child’s SSN and you have no idea who they are, that is identity theft, and the right form is Form 14039, Identity Theft Affidavit. Form 14039 can be filed on behalf of a dependent child when their SSN was used without your permission by an unknown person.3Internal Revenue Service. When to File an Identity Theft Affidavit
One exception overrides both: if the IRS has already contacted you with Letter 5071C, 4883C, or 5747C, follow the instructions in that letter instead of filing either form on your own.3Internal Revenue Service. When to File an Identity Theft Affidavit
Make Sure You Actually Qualify to Claim the Child
Before reporting anyone, confirm you pass the IRS tests. If you lose the dispute, you face the same penalties the other person would, which can include a multi-year ban on certain credits.
A qualifying child must meet all four tests: relationship (your son, daughter, stepchild, adopted child, foster child, sibling, half-sibling, stepsibling, or a descendant of any of them, including grandchildren, nieces, and nephews), age (under 19 at year end, or under 24 if a full-time student for at least five months, with no age limit if permanently and totally disabled), residency (lived with you more than half the year), and support (did not provide more than half of their own support). The child also cannot file a joint return with a spouse except solely to claim a refund.4Office of the Law Revision Counsel. 26 U.S.C. 152 – Dependent Defined5Internal Revenue Service. Dependents
When two people both qualify, the IRS applies tie-breaker rules in a fixed order: a parent beats a non-parent; between parents who do not file jointly, the one with whom the child lived more nights wins; if nights are equal, the parent with the higher adjusted gross income wins; if no parent claims the child, the non-parent with the higher AGI wins.6Internal Revenue Service. Tie-Breaker Rule
Divorced or Separated Parents
The custodial parent — the one the child lived with more nights — holds the default right to claim the child. A custodial parent can release that right to the other parent by signing Form 8332, which the noncustodial parent must attach to their return for each year they claim the child.7Internal Revenue Service. Form 8332 – Release/Revocation of Release of Claim to Exemption for Child by Custodial Parent A divorce decree alone does not substitute for Form 8332. If your ex claimed the child without a signed release, the tie-breaker rules work in your favor as the custodial parent.8Internal Revenue Service. About Form 8332 – Release/Revocation of Release of Claim to Exemption for Child by Custodial Parent
Evidence That Decides These Cases
Residency is where most dependent disputes are won or lost. The IRS will eventually ask one or both filers to prove the child lived with them more than half the year. Start gathering records as soon as you realize there’s a problem, because the response window after the IRS notice arrives can be tight.
- School enrollment forms or report cards showing your home address
- Medical or dental records listing your address as the child’s
- Daycare or childcare provider statements
- A letter from a landlord, property manager, or social services agency confirming the child lived with you
- Insurance records, religious organization records, or official mail addressed to the child at your home
What Happens After You File
Once the IRS processes your paper return and sees the same SSN on two returns, it flags the conflict. Both filers typically receive Notice CP87A, which tells each person that another taxpayer claimed the same dependent. The notice does not identify the other filer.9Internal Revenue Service. Understanding Your CP87A Notice
The notice sets a deadline for your response. If you are confident in your claim, you do not need to amend your return; just send in copies of your residency evidence by the deadline. Ignore the notice and the IRS can disallow your claim by default.
The review that follows is a narrow inquiry into who qualifies, not a full audit. Expect several months. Paper returns alone can take six months or more during busy periods, and the dispute adds more time. Any refund tied to the dependent will be held until the IRS resolves the case.10Internal Revenue Service. Identity Theft Dependents
Consequences for the Person Who Loses
Whoever loses the dispute has their return adjusted. They owe back the tax benefits they received, including any Child Tax Credit (worth up to $2,200 per child for tax year 2025), Earned Income Tax Credit, and head-of-household benefits, plus interest from the original due date.11Internal Revenue Service. Tax Credits for Individuals
The IRS can also impose an accuracy-related penalty equal to 20% of the underpayment if the claim resulted from negligence or disregard of the rules.12Office of the Law Revision Counsel. 26 U.S.C. 6662 – Imposition of Accuracy-Related Penalty on Underpayments Repayment, penalties, and interest together can run into thousands of dollars.
The penalties get steeper for intentional wrongdoing. A claim found to be due to reckless or intentional disregard of the rules triggers a two-year ban from the Child Tax Credit. A claim found to be fraudulent triggers a ten-year ban. Similar bans apply to the Earned Income Tax Credit, and after any disallowance the taxpayer must provide additional documentation before claiming the credit again.13Office of the Law Revision Counsel. 26 U.S.C. 24 – Child Tax Credit
These rules cut both ways. If the IRS determines the other person had the right to claim your child, your return is the one adjusted, and the same penalties and bans can apply to you.
Prevent It Next Year With an IP PIN
After the dispute is resolved, enroll your child in the IRS Identity Protection PIN program. An IP PIN is a six-digit number the IRS issues each year. Any return listing your child as a dependent must include the correct IP PIN or the IRS rejects it, which blocks unauthorized claims before they are processed.14Internal Revenue Service. Get an Identity Protection PIN (IP PIN)
Parents can request an IP PIN for a dependent child. For children under 18, the standard online enrollment is not available; you can submit Form 15227 online or schedule an in-person appointment at a local Taxpayer Assistance Center with two forms of identification for the child, such as a birth certificate and Social Security card.14Internal Revenue Service. Get an Identity Protection PIN (IP PIN)
An IP PIN also helps the following filing season. If the primary taxpayer on your return has a current-year IP PIN, you can e-file even when the dependent’s SSN was already used on another return, which avoids the paper-filing delay entirely.1Internal Revenue Service. Age, Name or SSN Rejects, Errors, Correction Procedures
If the Case Stalls
Dependent disputes can drag for months with your refund frozen the whole time. If the delay is causing financial hardship, or the IRS has not responded within 30 days of a promised date, contact the Taxpayer Advocate Service at 1-877-777-4778. TAS is an independent organization within the IRS that helps when normal channels fail, and it prioritizes cases involving economic harm, imminent adverse IRS action, or systemic delays.