The SS-8 gets filed by mail, separate from your return. From the IRS:
"Send the completed and signed Form SS-8 to:
Internal Revenue Service
Form SS-8 Determinations
P.O. Box 630
Stop 631
Holtsville, NY 11742-0630
Faxed, photocopied, or electronic versions of Form SS-8 are not acceptable for the initial request for the Form SS-8 determination. Do not submit Form SS-8 with your tax return as that will delay processing time."More info here:
https://www.irs.gov/instructions/iss8/ch01.html
