A small business set-aside reserves a federal contract so that only small businesses may compete for it. It is the most common way small firms win government work — and it turns on one deceptively simple test the contracting officer must apply. Understand the Rule of Two, the dollar thresholds that trigger an automatic reserve, and how your size is determined, and you will read a solicitation the way a contracting officer does. This page is educational, not legal advice — always verify against FAR Part 19, the SBA, and the specific solicitation in front of you.
The Rule of Two
The single decision that determines whether a contract is set aside for small business.
A general small business set-aside exists because of one rule. Under FAR 19.502-2, a contracting officer (CO) must set an acquisition aside for small business when there is a reasonable expectation that offers will be obtained from at least two responsible small business concerns, and that award will be made at fair-market prices. That is the “Rule of Two.”
The word that does the heavy lifting is responsible. Two small firms have to be expected to actually bid — capable, ready, and competitive — not merely exist somewhere in the database. COs reach that expectation through market research: prior procurement history, capability statements, responses to Sources Sought notices and Requests for Information, and who is registered and active under the relevant code.
If, after a set-aside, the CO receives only one acceptable offer from a responsible small business, award can still be made to that firm. If no acceptable small business offers come in, the set-aside is withdrawn and — if the requirement is still valid — it is resolicited on an unrestricted basis. The Rule of Two is a forward-looking expectation, not a guarantee.
The Automatic Reserve
Where the Rule of Two becomes the default rather than a judgment call.
Two dollar figures define a band where small business participation is the presumption. Acquisitions with an anticipated value above the micro-purchase threshold but at or below the Simplified Acquisition Threshold (SAT) are generally reserved exclusively for small business — unless the CO determines there is not a reasonable expectation of obtaining offers from two or more competitive, responsible small firms. In other words, inside this band the set-aside is the default, and the CO must affirmatively find the Rule of Two unmet to go unrestricted.
Micro-Purchase Threshold
The lower edge of the reserve band. Effective October 1, 2025, the micro-purchase threshold is $15,000 (raised from $10,000). Acquisitions at or below this floor use micro-purchase procedures.
Simplified Acquisition Threshold
The upper edge of the reserve band. Effective October 1, 2025, the SAT is $350,000 (raised from $250,000). These figures adjust periodically for inflation — verify the current numbers against acquisition.gov.
Above the SAT, the reserve is no longer automatic, but the Rule of Two still governs: the CO shall set the acquisition aside for small business whenever the same two-responsible-firms-at-fair-prices expectation is met. The threshold changes the default posture; it does not switch the rule off.
Total vs. Partial Set-Asides
A requirement can be reserved in whole, or carved into a small-business piece and an open piece.
FAR Subpart 19.5 recognizes more than one shape. A total set-aside reserves the entire acquisition for small business — every offeror must qualify as small. A partial set-aside splits a single requirement into two portions: one reserved for small business and one competed without restriction. Partial set-asides are used when a requirement is severable into discrete portions and the Rule of Two can be met for at least one of them, but not necessarily for the whole.
| Type | What is reserved | Who competes |
|---|---|---|
| Total set-aside | The entire acquisition | Small businesses only |
| Partial set-aside | A defined portion of a severable requirement | Small businesses on the reserved part; open competition on the rest |
Beyond these general set-asides sit the socioeconomic programs — 8(a), HUBZone, Service-Disabled Veteran-Owned, and Women-Owned Small Business — which reserve work for specific certified categories of small business rather than for small business broadly. They follow their own order of precedence and their own Rule-of-Two analysis. We cover those separately in the federal set-aside programs guide.
Size Standards & Self-Certifying in SAM
How “small” is defined — and how you claim it.
Whether you are “small” is not a single number. It is determined by the NAICS code the contracting officer assigns to the solicitation, and each NAICS code carries its own size standard — expressed either as a maximum average annual receipts figure or a maximum number of employees. For most IT and software services codes, including NAICS 541511 (Custom Computer Programming Services), the standard is a revenue cap averaged over a defined look-back period. A firm can be “small” under one code and “large” under another in the very same solicitation cycle.
How you claim size: self-certification
For a general small business set-aside, you do not file paperwork with the SBA to prove you are small. You self-certify in your SAM.gov registration. SAM walks you through each NAICS code in your profile and asks whether you meet that code’s size standard; your representations and certifications then travel with every offer you submit.
- Confirm the solicitation’s NAICS code and its current size standard before you bid.
- Keep your SAM reps and certs current — they are made under penalty of false certification.
- Calculate receipts or employees the way SBA’s rules require (look-back periods and affiliation count).
Picking the right code and reading its size standard is foundational; see our guide to NAICS codes for IT contractors, then watch the live board of federal IT opportunities for set-asides you can actually win.