1. Introduction: What is Form 15100?

IRS Form 15100, officially titled Adoption Taxpayer Identification Number (ATIN) Extension Request, is an administrative tax form published by the Internal Revenue Service (IRS). It is governed by the Wage and Investment Division of the IRS and handled specifically by the specialized ATIN Unit at the IRS Austin Service Center.

This form is used by adoptive parents who have an open, pending domestic adoption in the United States. When a child is legally placed in a home for adoption, parents often cannot obtain the child’s Social Security Number (SSN) before filing their tax returns, so they obtain a temporary Adoption Taxpayer Identification Number (ATIN) using Form W-7A. Because an ATIN automatically expires after two years, Form 15100 allows adoptive parents to request a one-year extension of their child’s ATIN so they can continue claiming eligible tax benefits while the adoption remains pending.

2. Purpose of the Form: Why Does Form 15100 Exist?

Domestic legal adoptions can be complex, involving extensive home studies, birth parent rights termination proceedings, and court delays. While waiting for a final adoption decree, adoptive parents cannot obtain an official Social Security card for the child from the Social Security Administration, and state placement agencies often keep the birth parents’ records confidential.

The IRS issues a temporary nine-digit ATIN (beginning with the number 9) to bridge this gap, but federal regulations limit an ATIN’s validity to exactly two years. If legal proceedings extend beyond that two-year window, an expired ATIN causes electronic tax returns to bounce and jeopardizes tax benefits. Form 15100 solves this problem by:

Extending the ATIN for One Year: It provides a formal legal avenue to keep the temporary identification number active for an additional 12 months while court proceedings finalize.
Preserving Valuable Adoption Tax Benefits: An active ATIN allows adoptive parents to claim the child as a dependent, claim the Adoption Tax Credit (Form 8839), and utilize the Child and Dependent Care Credit (Form 2441).
Transitioning to an SSN: If the child has finally been assigned a Social Security Number, Form 15100 also allows parents to notify the IRS so the temporary ATIN can be retired cleanly.

3. Who Needs to File This Form?

Form 15100 is not a general tax form for everyday taxpayers. It applies strictly to families in the process of domestic adoptions. You need to file Form 15100 if:

You previously applied for and received an Adoption Taxpayer Identification Number (ATIN) for a child legally placed in your home for domestic adoption.
Your child’s two-year ATIN is approaching its expiration date, or you received an IRS expiration notice (such as Notice CP 560 or CP 561).
The adoption is still pending, or the final decree was entered but you have not yet received an official Social Security Number for the child.
You need to maintain an active tax ID to file your federal income tax return and claim allowable adoption-related tax credits.

4. Who Is Exempt / Not Required to File?

Many adoptive families and taxpayers will never need to use Form 15100. You are exempt or not required to submit it under the following circumstances:

Applying for an Initial ATIN: If you need a brand-new ATIN for a child newly placed in your care, do not file Form 15100. You must file Form W-7A (Application for Taxpayer Identification Number for Pending U.S. Adoptions) instead.
Child Already Has an SSN: If the child already has a Social Security Number issued by the Social Security Administration, you do not need an extension. Use Form 15101 to report the new SSN to the IRS.
International Adoptions: Form 15100 is strictly for domestic adoptions. Children adopted internationally who are not yet U.S. citizens or permanent residents do not qualify for an ATIN; they must obtain an Individual Taxpayer Identification Number (ITIN) using Form W-7.
Adoptions Finalized Within Two Years: If your domestic adoption was completed and an SSN was assigned before the original two-year ATIN expired, no extension is required.

5. When to File: Deadlines and Frequency

Form 15100 is an event-based administrative filing rather than an annual recurring tax return. It should be submitted as soon as you realize your adoption will not be final before the two-year ATIN window closes.

Best practices recommend submitting Form 15100 approximately 60 to 90 days before your current ATIN expires, or immediately upon receiving an IRS Notice CP 560 warning of impending expiration. Do not wait until the spring tax filing deadline: if your ATIN lapses, your tax return will be rejected by IRS electronic filing systems. The IRS Austin Service Center generally takes 30 to 60 days to process the extension and mail an official extension confirmation notice.

6. Where and How to File

Form 15100 cannot be submitted through retail tax preparation software or commercial e-file systems. It must be delivered directly to the specialized IRS ATIN Unit by fax or mail:

Submission by Facsimile (Fastest Method): The quickest way to submit Form 15100 is by faxing the completed, signed form along with current placement documentation directly to the dedicated IRS ATIN fax number at 855-250-1731.
Submission by Standard Mail: If mailing via the U.S. Postal Service, send the paper package to the designated IRS address as per instructions (Internal Revenue Service, Stop 6182, Austin, TX 73301-0066).
Submission by Overnight Courier: If using a private delivery service (such as FedEx or UPS), use the physical street address as per instructions (Internal Revenue Service, 3651 S. Interregional Hwy 35, Stop 6182, Austin, TX 78741).
Original Ink Signatures: The IRS strictly requires original ink signatures from both adoptive parents; digital signatures generated by standard PDF viewers may be rejected.

7. Step-by-Step Instructions to Fill Form 15100

Form 15100 is a single-page document. Because an error can cause the IRS to delay your extension and reject your tax return, every section must be completed with accuracy. The table below outlines each primary section.

Section	Field Description	Required Information & Instructions
Part 1	Contact Information	Full legal names of adoptive parents, Taxpayer Identification Numbers (SSNs), address, and phone numbers.
Part 2	Circumstance Selection	Checkbox selecting: (1) SSN received, (2) One-year extension requested, or (3) Unable to obtain SSN.
Part 3	Adoption Status	Status checkboxes: “Adoption is final”, “Adoption is pending”, and confirmation of enclosed placement documents.
Part 4	Signatures	Original ink signatures, printed legal names, and execution dates for both adoptive parents.

Part 1: Contact Information

Enter the full legal names of up to two adoptive parents exactly as they appear on your federal tax returns. Provide each parent’s Social Security Number (SSN) or Individual Taxpayer Identification Number (ITIN). Enter your current mailing address; if your address changed since you originally filed Form W-7A, enter your new address here to update IRS records. Provide a primary and secondary daytime telephone number and indicate the best time of day to call.

Part 2: Circumstance Selection

You must check the single box that accurately describes your current situation:

Box 1 (Received an SSN): Check this box if the child was assigned an SSN. Enter the child’s legal name and their newly assigned nine-digit Social Security Number so the IRS can retire the ATIN.
Box 2 (Need a One-Year Extension): Check this box if the adoption is still pending. Enter the child’s name, their current nine-digit ATIN, and provide a clear written reason explaining why the extension is necessary (e.g., “Court hearing postponed,” “Contested parental rights proceedings,” or “Awaiting final state adoption decree”).
Box 3 (Unable to Obtain an SSN): Check this box if the adoption finalized, but state vital statistics or the SSA has not yet issued the child’s Social Security card. Enter the child’s name, their ATIN, and the specific reason.

Part 3: Adoption Status and Placement Documentation

Indicate whether the adoption is legally final or still pending by checking the appropriate box. You must also check the box confirming that you have enclosed placement documentation. You must attach an updated document signed by the child placement agency, county social services, or adoption attorney verifying that the child remains legally placed in your home.

Part 4: Original Signatures of Adoptive Parents

Both adoptive parents listed in Part 1 must sign and date the form in original ink and print their names clearly. If only one parent was listed on the original Form W-7A, only that parent signs. Incomplete signatures will cause the IRS to return the form unprocessed.

8. Required Documents and Information Needed Before Filling

Before preparing Form 15100, assemble the following legal and identification records:

The original IRS letter or notice (such as Notice CP 560 or CP 561) showing the child’s current nine-digit ATIN.
Updated Placement Documentation: A signed, dated letter or court document from the authorized child placement agency, state welfare department, or adoption attorney certifying that the child remains in your home for ongoing legal adoption.
Both adoptive parents’ Social Security Numbers and current contact details.
The child’s Social Security card (only if reporting that an SSN was received).

9. Common Mistakes to Avoid

Errors on Form 15100 can cause your child’s tax ID to lapse during tax season. Watch out for these frequent mistakes:

Filing Form 15100 to Apply for an SSN: The IRS cannot assign or issue a Social Security Number. SSNs are issued exclusively by the Social Security Administration through Form SS-5. Form 15100 only extends an IRS temporary tax number.
Using Form 15100 Instead of Form W-7A: You cannot use Form 15100 to apply for an initial ATIN. Form 15100 is strictly for extending an existing number that was previously issued under Form W-7A.
Missing the Second Parent’s Signature: If two parents are listed on the form, both parents must sign in ink. Submitting a form with only one signature is a primary cause of processing delays.
Omitting Updated Placement Documents: Submitting Form 15100 without updated placement agency paperwork will prompt the IRS to send an inquiry letter, pausing your extension request.
Mailing Courier Packages to the P.O. Box: Private couriers (FedEx, UPS) cannot deliver to IRS postal stops. If using an overnight courier, use the physical street address (3651 S. Interregional Hwy 35) to prevent returned packages.

10. Penalties for Non-Filing or Errors

While Form 15100 does not carry direct statutory tax penalties, failing to submit it carries severe financial consequences on your annual tax return:

Rejection of Electronic Tax Returns: If you attempt to e-file a tax return using an expired ATIN, IRS e-file servers will automatically reject the return with a dependent identification mismatch error.
Loss of Valuable Tax Credits: If your return is processed on paper with an expired ATIN, the IRS will disallow your dependency claims, strip away the Child and Dependent Care Credit, and eliminate the Adoption Credit, potentially costing you thousands of dollars in refunds.
Delayed Tax Refunds: An expired ATIN triggers IRS math error notices, freezing your refund for months while you scramble to resolve the child’s identification status.
Perjury Consequences: Form 15100 is signed under penalties of perjury. Falsifying adoption status or claiming children not legally placed in your home is a federal crime punishable under 26 U.S.C. Section 7206.

11. Related Forms or Schedules

Form 15100 operates within a specialized family of adoption and taxpayer identification forms:

Form W-7A: Application for Taxpayer Identification Number for Pending U.S. Adoptions (the original application).
Form 15101: Provide a Social Security Number (SSN) for Adoptive Child (used to report a newly received SSN).
Form 8839: Qualified Adoption Expenses (used to claim the federal adoption tax credit).
Form 2441: Child and Dependent Care Expenses (eligible for use with an active ATIN).
Form SS-5: Application for a Social Security Card (filed with the Social Security Administration once adoption is final).
Notice CP 560 / Notice CP 561: IRS notices alerting parents of an expiring ATIN.
Form 8822: Change of Address.

12. Frequently Asked Questions (FAQs)

1. How long is an ATIN extension valid for?

An extension granted under Form 15100 is valid for one additional year. If your adoption remains pending after the extension year ends, you must contact the IRS ATIN Unit to explain the extenuating legal circumstances.

2. Can I claim the Child Tax Credit (CTC) or Earned Income Tax Credit (EITC) with an ATIN?

No. Under federal tax law, both the Child Tax Credit and the Earned Income Tax Credit strictly require the child to have a valid Social Security Number issued on or before the due date of the tax return. An ATIN can only be used to claim the child as a dependent, claim the Credit for Other Dependents ($500), claim the Child and Dependent Care Credit, and claim the Adoption Tax Credit (Form 8839).

3. Can I file Form 15100 online?

No. Form 15100 is not eligible for electronic filing. You must print, complete, and sign the form in original ink, and submit it to the IRS Austin Service Center via fax or mail.

4. Does an ATIN apply to international adoptions?

No. An ATIN is strictly for children in domestic U.S. adoptions. Children adopted from foreign countries who do not yet have an SSN must apply for an Individual Taxpayer Identification Number (ITIN) using IRS Form W-7.

5. What should I do if our child receives an SSN while our extension is pending?

If the Social Security Administration assigns an SSN while your extension is under review, you should immediately file Form 15101 (or submit Form 15100 with Box 1 checked) providing the newly assigned SSN so the IRS can deactivate the temporary ATIN.

6. What happens if only one parent signs Form 15100?

If two adoptive parents were listed on the original Form W-7A application, the IRS will reject Form 15100 if it contains only one signature. Both parents must sign and date the extension request in ink.

13. Conclusion: Key Takeaways

IRS Form 15100 is an indispensable administrative lifeline for families navigating lengthy domestic adoptions. By requesting a one-year extension of an expiring Adoption Taxpayer Identification Number, adoptive parents ensure their child’s temporary tax ID remains active, preventing electronic filing rejections and protecting valuable adoption tax benefits.

Because processing takes several weeks and requires current third-party placement documentation, adoptive parents should submit Form 15100 approximately 60 to 90 days before their two-year ATIN expires and ensure both parents provide original ink signatures before faxing or mailing the request.

IRS Form 15100 Guide: ATIN Extension Request Instructions