You filed your tax return, claimed your child, and started planning around the refund. Then a letter from the IRS shows up saying another taxpayer claimed the same dependent — with the same Social Security number — on their return. Your stomach drops. Are you being audited? Is someone stealing your child's identity? Do you owe money?
Take a breath. That letter is almost certainly Notice CP87A, and it is one of the most misunderstood letters the IRS sends. It is not an audit, it is not a bill, and in many cases the correct response is to do nothing at all. But in other cases it is an early warning that you need to fix your return before a small problem turns into back taxes, interest, and lost credits. Here is how to tell which situation you are in and exactly what to do about each one.
What CP87A Actually Is
CP87A means the IRS received two different tax returns claiming the same person — identified by Social Security number — as a dependent or qualifying child. The notice lists the last four digits of the Social Security number it is concerned about so you can check which dependent triggered it.
Three things the notice is telling you up front:
- You are not being audited. The notice says this explicitly. It is a heads-up that two claims exist, not the start of an examination.
- The IRS will not tell you who the other person is. Disclosure laws prohibit it. In most cases you can guess — a former spouse, the child's other parent, a grandparent who helps out — but the letter itself will never name them.
- You do not need to prove anything right now. If you are entitled to claim the dependent, the instructions say you do not need to write back or send any documents. Keep the notice for your records and move on.
That last point surprises people. The instinct is to immediately mail the IRS a stack of birth certificates and school records. Unless the IRS specifically asks for them later, that package goes nowhere useful. Your first job is narrower: figure out whether the duplicate claim is a typo, a legitimate dispute you will win, or a mistake on your return that you need to fix.
Step 1: Check the Social Security Number
Before anything else, compare the last four digits on the notice against the actual Social Security card of the dependent you claimed.
If the numbers do not match what is on the card, the mystery is solved: you mistyped a dependent's Social Security number on your return, and your typo happened to duplicate a real number someone else claimed. The IRS says you do not need to contact them or take any action. Just use the correct number on your next return. (If the wrong number meant you claimed credits you were not entitled to, that is a separate issue worth discussing with a tax preparer — but the duplicate-claim problem itself is over.)
If the numbers match, move on to the real question: are you actually entitled to claim this dependent?
Step 2: Run Through the Qualifying Child Tests
Most duplicate claims involve a child, so work through the five tests from IRS Publication 501 that define a qualifying child. Your child must meet all five:
- Relationship. Your son, daughter, stepchild, foster child, sibling (or a descendant of any of them) — or an adopted child.
- Age. Under 19 at year-end (under 24 if a full-time student for at least five months), or any age if permanently and totally disabled.
- Residency. Lived with you for more than half the year. Temporary absences for school, medical care, or vacation still count as living with you — but there are specific exceptions, including for divorced or separated parents, covered below.
- Support. The child did not provide more than half of their own support during the year.
- Joint return. The child is not filing a joint return with a spouse (with a narrow exception when the joint return is filed only to claim a refund of withheld tax).
If your dependent is an adult relative rather than a child — an aging parent, for example — a different set of qualifying-relative tests applies, including a gross-income ceiling and a support test where you must provide more than half of their support.
Be honest with yourself on the residency and support tests, because those are where most losing claims fail. A child who lived with their other parent ten months of the year, or a teenager who earned enough working full-time to support themselves, will not survive IRS scrutiny no matter how strongly you feel they are "your" dependent.
If You Are Entitled to Claim the Dependent: Do Nothing
This is the outcome people find hardest to believe. If you reviewed the tests and you are confident the dependent is yours to claim, the IRS instructions are explicit: you do not need to write, call, or send anything. Keep the notice with your tax records in case questions come up later, and consider reviewing it with your tax preparer if you used one.
Do not file an amended return "just to be safe." An unnecessary amendment can slow things down and create confusion. The duplicate claim is the other filer's problem to resolve, not yours.
If You Claimed Someone by Mistake: File Form 1040-X
If the tests show the dependent does not qualify — the residency math does not work, the support test fails, or you realize an ex-spouse had the right to claim the child this year — you need to correct your return by filing Form 1040-X, Amended U.S. Individual Income Tax Return. Mail it to the IRS service center shown in the form's instructions.
A few practical notes on amending:
- Expect it to take a while. Amended returns are processed by hand, and current processing times routinely stretch many months. File promptly rather than waiting.
- Removing a dependent usually means repaying money. Your tax goes up, and credits tied to the dependent — the child tax credit, earned income credit, dependent-care benefits — shrink or disappear. Interest accrues on any additional tax from the original due date of the return, so the sooner you amend, the less interest you owe.
- Fix your records going forward. If the error came from a custody schedule, an aging-out child, or a support change, update whatever system you use to track this so next year's return starts from correct facts.
Voluntarily correcting the return is far cheaper than waiting for the IRS to disallow the claim through examination, when penalties can join interest on the bill.
The Divorced-Parent Trap: Custody Schedules vs. Tax Rules
The single most common source of duplicate dependent claims is divorced, separated, or never-married parents who each believe this is "their year" to claim the child. Three rules decide these cases, and they surprise a lot of people:
Nights win, not court orders. The custodial parent — the one with whom the child spent the greater number of nights during the year — generally claims the child. A state court order or divorce decree awarding the exemption to the noncustodial parent does not bind the IRS. If your decree says you get to claim your daughter in even years but she lived with her mother 300 nights that year and there is no signed release, the IRS sides with the mother.
The release has to be in writing. The custodial parent can hand the claim to the noncustodial parent by signing Form 8332 (or a substantially similar written declaration) and the noncustodial parent must attach it to their return. A verbal agreement, a text message thread, or a line in the divorce decree is not enough for the IRS.
The release transfers less than people think. Form 8332 transfers the dependency exemption and the child tax credit, additional child tax credit, and credit for other dependents. It does not transfer the earned income credit, head-of-household filing status, the dependent-care credit, or the exclusion for dependent-care benefits. Those stay with the custodial parent even when the noncustodial parent properly claims the child.
If you co-parent, the cheapest insurance against a CP87A is a written agreement made before filing season: who claims the child which years, a signed Form 8332 exchanged on time, and a shared calendar documenting overnights. Most duplicate claims between parents are communication failures, not fraud.
The Tie-Breaker Rules: How the IRS Picks a Winner
When two taxpayers both claim the same child and neither backs down, the IRS applies statutory tie-breaker rules. Knowing them tells you whether a fight is worth having:
- Parent beats non-parent. If only one claimant is the child's parent, the parent wins.
- Between parents who do not file jointly, residency decides. The parent with whom the child lived longest during the year wins.
- Equal time goes to higher income. If the child split time evenly between parents, the parent with the higher adjusted gross income wins.
- If no parent claims the child, the non-parent claimant with the highest AGI wins — but only if their AGI exceeds that of any parent who could have claimed the child.
Run your facts through that ladder before deciding to stand your ground or amend. If you are a grandparent who had the kids every summer but they lived with their mother the rest of the year, the tie-breakers will not save the claim.
The E-File Rejection Problem (and the IP PIN Fix)
Many people first learn about a duplicate claim the hard way: their e-filed return gets rejected because the dependent's Social Security number already appears on another filed return. The IRS computer simply refuses to accept the same dependent twice.
Starting with the 2025 filing season, there is a way through. If the primary taxpayer on the second return includes a valid Identity Protection PIN (IP PIN) — the six-digit number available through an IRS Online Account — the IRS will accept the e-filed return even though the dependent was already claimed elsewhere. A spouse or the dependents themselves do not need IP PINs for this to work; the primary taxpayer's PIN is what unlocks the return. If your return rejects for a duplicate dependent and you do not have an IP PIN, get one and e-file again with it entered.
Two caveats: prior-year duplicate-dependent returns generally still have to be paper-filed, and getting your return accepted is not the same as winning the claim. Acceptance just gets both returns into the system; the tie-breaker process still decides who keeps the dependent.
Everyone in a shared-custody situation should consider getting an IP PIN for themselves — and IP PINs are also available for dependents. It costs nothing, it blocks identity thieves from filing with your number, and it is now the fastest path past a duplicate-dependent rejection.
When It Might Be Identity Theft
Sometimes the duplicate claim has nothing to do with family. Red flags for identity theft include receiving a CP87A for a year you never filed, or for a dependent whose number you never gave to anyone outside your household.
In that case, call the number shown on the notice and review the IRS Identity Theft Central guidance. Getting an IP PIN is especially important here: it locks your Social Security number so the thief cannot file with it again next year. Keep a file with the notice, the date you called, and any case numbers — identity-theft resolutions take time, and you will want a paper trail.
What Happens If Neither Side Backs Down
If both taxpayers stand firm, the IRS examines both returns and applies the tie-breaker rules. The loser receives a notice disallowing the dependent and the associated credits, and owes the additional tax plus interest — and potentially accuracy-related penalties.
Losing has a tail, too. If your earned income credit, child tax credit, additional child tax credit, credit for other dependents, or American opportunity credit is reduced or disallowed for anything other than a math or clerical error, you must attach Form 8862 to a future return before you can claim those credits again. In other words, an audit loss does not just cost you this year's credit — it adds paperwork to every future claim until you clear the requirement.
This is why the honest self-assessment in Step 2 matters so much. Amending voluntarily costs you the credit and some interest. Losing an examination can cost you the credit, interest, penalties, and a Form 8862 filing requirement for years to come.
Avoiding a Repeat Next Year
- Use the Interactive Tax Assistant. The IRS "Whom May I Claim as a Dependent?" tool walks through the tests for your specific situation before you file.
- Coordinate before filing season. In shared-custody families, confirm in writing who claims the child, exchange any needed Form 8332 early, and agree on who files first.
- Keep residency proof as you go. School records, medical records, childcare statements, and a simple overnight calendar are what win residency disputes. Reconstructing them a year later is painful.
- Track support with real numbers. If you provide most of a dependent relative's support, keep the receipts and a running total — grocery bills, rent payments, medical costs — in one place throughout the year rather than estimating at tax time.
- Get IP PINs for the family. It is free, takes one identity-verification session, and prevents both fraud and e-file rejections.
That record-keeping point deserves emphasis, because it is where tax compliance quietly lives or dies. Residency calendars, support-payment logs, custody agreements, and signed releases are all just organized financial records. Taxpayers who track money and dates contemporaneously — as they happen, in a system they control — resolve CP87A situations in an afternoon. Taxpayers who reconstruct from memory spend months. Whether you use a spreadsheet or a full accounting setup, the habit of logging support payments and keeping family financial documents in one searchable place pays for itself the first time any notice arrives.
Simplify Your Financial Management
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