Mailing and fax details
The standard and overnight IRS addresses in Austin, TX, a fax number, and a phone number for questions.
15100
Adoption Taxpayer Identification Number (ATIN) Extension Request
- Agency
- IRS
- Revision
- Rev. 10-2017
- Fillable fields
- 36
- Pages
- 1
- Official source
- IRS form page
- Checked
- October 21, 2026
Form 15100: Adoption Taxpayer Identification Number (ATIN) Extension Request
Form 15100, Adoption Taxpayer Identification Number (ATIN) Extension Request, is a one-page IRS form completed by adoptive parents who have an ATIN for an adoptee. On it, the parents tell the IRS which of three circumstances applies: they received a social security number for the adoptee, they need a 1 year extension of the ATIN, or they could not get a social security number for the adoptee.
The form also asks for contact information, the status of the adoption (final or pending), and the original signatures of the adoptive parents. It says to complete the form and fax or mail it to the IRS in Austin, Texas.
No separate instructions are linked for Form 15100, so this page describes what the form itself prints. You can fill out the PDF free in your browser on this page and download it without an account.
What's on Form 15100
Contact information
Two lines for a name and taxpayer identification number, a new address if it changed, and primary and secondary phone numbers with the best time to call.
Circumstances
Three boxes: a social security number was received, a 1 year extension is needed, or a social security number could not be obtained, each with the adoptee's name and the SSN or ATIN.
Reason fields
A reason field under the extension box and under the box for not getting a social security number.
Status of your adoption
Boxes for My adoption is final and My adoption is pending, and a line about enclosing documents the placement agency or agent signed.
Signatures
Printed names, original signatures and dates for the adoptive parents.
How to fill out Form 15100
- 1
Contact information
Enter each name with its taxpayer identification number. Write a new address only if the address changed, then add phone numbers and the best time to call, marking a.m. or p.m.
- 2
Choose the circumstance
Check the box that applies: SSN received, 1 year extension needed, or SSN could not be obtained, and enter the adoptee's name.
- 3
Enter the number
For an SSN received, write the social security number assigned. For an extension or when no SSN was obtained, enter the ATIN assigned.
- 4
Give a reason
For an extension request, or when a social security number could not be obtained, write the reason in the space provided.
- 5
Adoption status and documents
Check final or pending. The form includes the line I am enclosing documents the placement agency or agent signed.
- 6
Sign
Print each adoptive parent's name, then sign with an original signature and date.
Why fill Form 15100 on indox
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Where to send it and contact details
Standard mail
The form lists Internal Revenue Service, Stop 6182, Austin, TX 73301-0066.
Overnight delivery
The form lists Internal Revenue Service, 3651 S. Interregional Hwy 35, Stop 6182, Austin, TX 78741.
Fax
The form lists fax number (855) 250-1731.
Questions
The form says questions can go to (737) 800-5511 and notes that this number is not toll free.
No deadline printed
The form does not print a filing deadline or a processing time.
Related forms
Who files Form 15100?
The form is completed and signed by adoptive parents and sent to the IRS. It refers to the adoptee by name and ATIN.
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Questions about Form 15100
What is Form 15100 for?
It is the Adoption Taxpayer Identification Number (ATIN) Extension Request. Adoptive parents use it to tell the IRS they received an SSN for the adoptee, need a 1 year extension of the ATIN, or could not get an SSN.
Where is Form 15100 sent?
The form says to fax or mail it. Standard mail goes to Internal Revenue Service, Stop 6182, Austin, TX 73301-0066, and the fax number is (855) 250-1731.
How long an extension does it request?
The extension box reads I need a 1 year extension for the named adoptee's ATIN, with space for the reason.
Who signs Form 15100?
The adoptive parents. The form asks for original signatures, with printed names and dates.
Is there a phone number for questions?
The form lists (737) 800-5511 and says it is not toll free.
Are there separate instructions?
No instructions document is linked for Form 15100. The form prints its own directions, addresses and fax number at the top.