What this notice is about Important Information about your child's Adoption Taxpayer Identification Number (ATIN) - We assigned your child an ATIN. What you need to do Complete Form 15101, Provide Social Security Number (SSN) for Adoptive Child PDF, included with your notice when you receive a Social Security number (SSN) for your child. Detach notice stub, mail it with Form 15101 in the envelope provided. If you prefer, you can fax it using the information provided on the form. You may want to Call us at the number listed in your notice. See additional information on Adoption Taxpayer Identification Number. Frequently asked questions How long is an ATIN useful? An ATIN is valid for 2 years. If you don't have an SSN for your child, you can request a 1 year extension. For more information, see instructions for completing a Form W-7A, Application for IRS Adoptions for IRS Individual Taxpayer Identification Number. Reference Tools Publication 1, Your Rights as a Taxpayer Full list of tax forms and instructions Need Help? You can authorize someone to contact the IRS on your behalf. See if you qualify for help from a Low Income Taxpayer Clinic. If you can’t find what you need online, call the IRS number at the top of your notice or letter.