Every federal solicitation carries a six-digit number that quietly decides who is allowed to compete. Under 13 CFR 121.402, the contracting officer designates a single NAICS code — the one that best describes the principal purpose of what is being bought — and with it a size standard. Land on the right side of that line and the set-aside universe opens up; land on the wrong side and you are competing against Lockheed. Yet size is one of the most misunderstood mechanics in federal contracting, partly because the rules changed three times in the past few years and most online guides never caught up.

The FAR mirrors the rule: FAR 19.102 requires one NAICS code and one size standard per solicitation, chosen for the component that accounts for the greatest share of contract value. Multiple-award contracts may be split into discrete categories, each with its own code, and every order under one draws its code from the underlying contract. If you think the CO picked a code that unfairly shapes the competition, that designation is appealable — to SBA's Office of Hearings and Appeals, on a short fuse after solicitation issuance.

Two yardsticks: receipts and headcount

Size standards come in two flavors. Services and construction industries are measured in average annual receipts; manufacturing and R&D industries in employees. Both averages are longer than people assume.

Receipts means total income plus cost of goods sold, per your tax returns, averaged over your most recently completed five fiscal years — the Small Business Runway Extension Act stretched the old three-year average, and the transition period ended in January 2022. A firm growing fast benefits: strong recent years are diluted by leaner early ones. Employee-based standards count everyone — full-time, part-time, temporary, and leased workers all count the same — averaged across all pay periods in the preceding 24 calendar months.

The dollar lines themselves sit in the 13 CFR 121.201 table: $34 million for custom computer programming and systems design (541511/541512), $25.5 million for engineering services (541330), $45 million for commercial building construction (236220), 1,000 employees for most physical-science R&D (541715), 1,300 for shipbuilding. The dollar figures reflect SBA's 13.65 percent inflation adjustment to all monetary size standards, effective December 2022, and have not moved since; the employee-based lines date from a separate rule effective March 2023 — but an August 2025 proposed rule would raise standards in 263 industries and adopt a policy of never lowering them (except to exclude firms dominant in their field). As of July 2026 that rule has not been finalized, so check the current table before certifying.

Affiliation: the size you don't know you have

SBA does not just measure your company — it measures everyone who controls you, whom you control, or who shares control with you, and adds their receipts or employees to yours. Under 13 CFR 121.103, it does not matter whether control is ever exercised; the power to control is enough, judged on the totality of the circumstances.

The classic tripwires: a majority owner with other businesses; common officers or directors across firms; family members whose companies do business with each other (presumed affiliated, rebuttably); economic dependence on a single customer for the lion's share of revenue; and the ostensible subcontractor rule, where a large subcontractor performing the primary and vital requirements of a contract — or one on which the prime is unusually reliant — converts the whole team into one large offeror. An SBA-approved mentor-protégé agreement is the notable safe harbor: assistance under it does not create affiliation by itself.

Recertification just got teeth

Size is normally locked in as of your offer date, but SBA's December 2024 rule — consolidated into 13 CFR 125.12 — tightened what happens afterward. You must recertify within 30 days of a merger, acquisition, or sale that changes controlling interest, and on long-term contracts before the end of year five and each option. The provision with real bite took effect January 17, 2026: if your company is acquired by or merges with a large business, a disqualifying recertification now makes you ineligible for future set-aside orders under your multiple-award contracts — not just uncountable toward agency goals. For sellers of small businesses holding set-aside MAC positions, that quietly repriced the deal.

Policing the line

Competitors enforce size rules more energetically than the government does. Any unsuccessful offeror can file a size protest — routed through the contracting officer to the SBA Government Contracting Area Office — but only within five business days of bid opening or notification of the apparent awardee. The protested firm must answer SBA Form 355 within three working days, and silence lets SBA presume the firm is other than small. Miss your five days and the award stands, however oversized the winner.

What It Means for Contractors

Check your math before every certification. Pull five fiscal years of returns, compute the average including cost of goods sold, and rerun it annually — firms drift over standards without noticing, and a false certification is False Claims Act territory. SBA's size standards tool and the downloadable table are the authoritative references; anything a consultant or an old blog post tells you is only as good as its date.

Map your affiliation exposure now, not during a protest. Document why minority investors lack control, keep family-business dealings at arm's length, and structure teaming so your subcontractor is not doing the contract's primary and vital work. If you are contemplating selling — or buying — a small business with set-aside multiple-award positions, price in the January 2026 recertification rules before signing. And watch the pending size-standard increases: for firms hovering just over a receipts line, the proposed rule for 263 industries could put them back under it. NAICS 2027, the next five-yearly revision of the codes themselves, is running behind its published schedule; the 2022 edition remains in force.

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