If you plan to adopt your foster child but the adoption will not be final by the time you need to file your tax return, AND if the social worker cannot give you the child’s social security number, you can use IRS Form W-7A “Application for Alternative Taxpayer ID Number” (or “ATIN”). This is intended for use by pre-adoptive parents who need a “temporary” tax ID number for a child who’s SSN number is either unknown to the taxpayer and/or the child’s social worker, or hasn’t been assigned yet by the Social Security Administration.
IRS Form W-7A is a fillable form available on the IRS website: IRS.gov
The IRS FAQs at https://www.irs.gov/
A.4. You should apply for an ATIN only if you are in the process of adopting a child and you meet all of the following qualifications:
The child is legally placed in your home for legal adoption by an authorized placement agency.
The adoption is a domestic adoption OR the adoption is a foreign adoption and the child/children have a Permanent Resident Alien Card or Certificate of Citizenship.
You cannot obtain the child’s existing SSN even though you have made a reasonable attempt to obtain it from the birth parents, the placement agency, and other persons.
You cannot obtain an SSN for the child from the SSA for any reason. (For example, the adoption is not final).
You are eligible to claim the child as a dependent on your tax return.