SIN (Special Item Number)

Full Definition

A Special Item Number (SIN) is a product or service classification code within the GSA Multiple Award Schedule (MAS) program that defines the specific categories a Schedule contract holder is authorized to sell to federal agencies. Each SIN maps to one or more NAICS codes and carries its own scope description, maximum order threshold, terms, and conditions. The GSA consolidated approximately 24 legacy schedules into a single MAS in 2019, reorganizing SINs into large categories covering professional services, IT, facilities, office products, scientific equipment, and more. Contractors select specific SINs during their GSA Schedule application and must demonstrate relevant experience and competitive pricing for each SIN requested. Adding new SINs to an existing Schedule contract requires a modification request to the GSA contracting officer.

Why It Matters

Selecting the right SINs during your GSA Schedule application is a strategic decision that defines your addressable market on the government's largest contract vehicle. Research which SINs government buyers use when purchasing services similar to yours by reviewing award data on USASpending.gov and GSA's eBuy portal. Holding multiple complementary SINs broadens your reach and allows you to respond to more RFQs. Government buyers search by SIN on GSA Advantage and eBuy, so your SIN selections directly determine your visibility. Small businesses should start with SINs where they have the strongest past performance and most competitive pricing, then add additional SINs through contract modifications as their portfolio grows.

Example

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