GSA MAS Large Categories and SINs: how the Schedule is structured today
TL;DR. Since the 2019-2020 consolidation, all GSA Schedule offerings live under one Multiple Award Schedule organized into 12 Large Categories. Each Large Category breaks into Subcategories, and each Subcategory contains one or more Special Item Numbers (SINs). Your Schedule contract is awarded for specific SINs, not for an entire category. Picking the right SINs is the single most important strategic decision in the Schedule-application process.
The 12 Large Categories
The current MAS structure organizes every offering into one of 12 top-level Large Categories. Each covers a broad area of federal buying.
| # | Large Category | Representative scope |
|---|---|---|
| 1 | Information Technology | IT hardware, software, services, cybersecurity, telecom, data centers (formerly most of Schedule 70) |
| 2 | Facilities | Facilities maintenance, grounds, pest control, cleaning, waste management |
| 3 | Furniture and Furnishings | Office, packaged office, healthcare, hospitality, laboratory, and household furniture |
| 4 | Human Capital | Staffing, recruiting, training services, HR consulting |
| 5 | Industrial Products and Services | Hardware, tools, MRO, industrial supplies, test and measurement |
| 6 | Miscellaneous | Items and services that do not fit cleanly elsewhere |
| 7 | Office Management | Office supplies, records management, document solutions, mail management |
| 8 | Professional Services | Management consulting, financial, environmental, R&D, engineering, logistics (formerly much of PSS) |
| 9 | Scientific Management and Solutions | Scientific equipment, laboratory services, test and measurement |
| 10 | Security and Protection | Security services, protection equipment, emergency response |
| 11 | Transportation and Logistics Services | Freight, delivery, relocation, fleet management, travel |
| 12 | Travel | Lodging, conferences, meetings, travel management |
Category numbers and scope are broadly stable but do get refined. Always confirm the current structure in the MAS solicitation before mapping your offerings.
What a SIN is
A Special Item Number is a specific product or service category nested inside a Subcategory, which is nested inside a Large Category. SINs are the unit of award on a Schedule contract. You apply for specific SINs, your contract covers those specific SINs, and buyers search for quotes by SIN on eBuy.
Examples to ground the concept:
- SIN 54151S — Information Technology Professional Services (under Large Category 1, Information Technology). Covers IT services like programming, systems integration, cybersecurity consulting.
- SIN 541611 — Management and Financial Consulting, Acquisition and Grants Management Support (under Large Category 8, Professional Services).
- SIN 561611 — Security Guard and Patrol Services (under Large Category 10, Security and Protection).
The last 5-6 digits of most SIN numbers match the corresponding NAICS code the SIN aligns with, which is useful when you are mapping your SAM NAICS codes to potential SIN targets.
Picking the right SIN(s)
SIN selection is consequential. Each SIN has its own scope, pricing template, labor-category conventions, and evaluation criteria. Pick the wrong SIN and you end up either unable to quote on the eBuy RFQs that matter to you, or priced in a way that does not map to the work you actually win.
A working approach:
- List your current commercial offerings in plain language. Not marketing copy; concrete deliverables. "Managed EDR service for mid-market financial services," not "innovative cybersecurity solutions."
- Look up comparable commercial vendors in GSA eLibrary. Find 3-5 companies doing similar work and note which SINs they hold. Peer-set pattern is the fastest way to narrow your SIN shortlist.
- Read each candidate SIN's scope description in the MAS solicitation. Scope language tells you what counts as an in-scope offering. Edge cases are real; borderline offerings get challenged at evaluation.
- Pull recent eBuy RFQ history for each SIN. If the agencies you target are not issuing RFQs under that SIN, the SIN is not a useful path. This check surfaces SINs that look right on paper but produce no real opportunities.
- Talk to a GSA contracting officer before committing. Most regions have a pre-offer consultation process. A 30-minute call can save weeks of wasted proposal work.
Adding or changing SINs after award
SINs can be added or dropped via Schedule modifications filed through eMod. Most holders end up making at least one modification in the first two years as their understanding of which SINs actually produce work sharpens.
Adding a SIN after award is lighter than adding one at initial proposal time, because many corporate-level components (past performance, financials, CSP narrative) do not need to be re-submitted. The SIN-specific pieces (additional pricing, specific past performance for the SIN scope, any SIN-specific certifications) do need to be submitted. Typical add-a-SIN timeline is 2-4 months.
Dropping a SIN is administratively simple but think twice. Once dropped, future eBuy RFQs under that SIN are invisible to you. Check the RFQ volume history before removing a SIN.
How category and SIN structure has changed
Pre-consolidation (before 2020), the Schedule program had 24 separate Schedules, each with its own solicitation, its own contracting officers, its own SIN numbering convention, and often its own catalog system. Schedule 70 was the IT schedule; Professional Services (PSS) covered consulting; 736 covered temporary staffing; and so on.
The 2019-2020 consolidation merged all 24 Schedules into a single MAS with the 12 Large Category structure above. Holders of the old Schedules were migrated ("novated") onto the single MAS. Their SINs were mapped into the new structure; in most cases the underlying offering stayed the same but the SIN numbers and structural position changed.
See our MAS consolidation page for the full history and what it means if you are encountering references to the old Schedules.
Frequently asked questions
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How many SINs are there?
Hundreds. The exact count changes as GSA refines the structure through MAS solicitation updates. The current MAS solicitation and GSA eLibrary are the authoritative sources. Do not rely on a third-party list from more than a year ago; SIN additions, retirements, and scope changes happen regularly.
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Can I hold multiple SINs on one contract?
Yes. Most holders hold multiple SINs. There is no cap. Multi-SIN holders can quote on a wider range of eBuy RFQs, but each SIN has its own compliance footprint (pricing, labor categories, scope).
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Do SIN numbers match NAICS codes?
Partially. The last 5-6 digits of most SIN numbers correspond to the related NAICS code. The leading digits identify the SIN within its Subcategory. Matching your SAM NAICS codes to candidate SINs is a reasonable starting point, but not every NAICS code has a matching SIN, and some SINs span multiple NAICS codes.
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What happened to Schedule 70?
Schedule 70 (the IT Schedule) was folded into the consolidated MAS in 2020 as Large Category 1, Information Technology. Most Schedule 70 SINs were migrated with some renumbering; the offerings stayed broadly the same but the structural position changed. See our Schedule 70 page for more detail.
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How do I find what SIN a specific offering falls under?
Two fastest paths. First, search GSA eLibrary for vendors doing similar work and check which SINs they hold. Second, read the Large Category scope descriptions in the current MAS solicitation to narrow the candidate list, then read each candidate SIN's scope paragraph. If both paths leave ambiguity, request a pre-offer consultation with a GSA contracting officer.
Sources: GSA eLibrary (SIN and contract search) , GSA MAS solicitation page , GSA Vendor Support Center .
Last updated 2026-04-22. This page is informational and is not legal or tax advice. Confirm current requirements with your GSA contracting officer, an APEX Accelerator counselor, or a qualified professional.