“Small business” isn’t a vibe — it’s a precise SBA determination, and it’s the gate to every set-aside you pursue. Two things decide it: the size standard for the work’s NAICS code, and the affiliation rules that can sweep other companies’ size into yours. Both trip up firms that assume they qualify.

Size standards are per NAICS

The SBA sets a size standard for each NAICS code, expressed one of two ways:

  • Revenue-based — average annual receipts under a dollar cap (common for services).
  • Employee-based — average number of employees under a headcount cap (common for manufacturing).

Because the standard attaches to the NAICS code, you can be small under one code and other than small under another. What matters on any given bid is whether you’re small under that solicitation’s assigned NAICS.

How the averages are calculated

Size isn’t a single year:

  • Receipts are generally averaged over a multi-year lookback (the rule has moved to a 5-year average for receipts-based standards).
  • Employees are generally averaged over a trailing 12 months.

So a single big year won’t instantly disqualify you, and a single lean year won’t instantly qualify you — it’s the average that counts. Check the current SBA size-standards table for the exact cap and method; they’re periodically updated.

Affiliation — the part that surprises people

Here’s the trap: SBA can count other companies’ size as part of yours if you’re affiliated — meaning one party controls, or has the power to control, the other (or a third party controls both). Control can come from ownership, management, common investors, economic dependence, or family relationships, among others. If you’re affiliated, your combined size is measured — which can push you over the standard even if your company alone is small.

Common affiliation pitfalls:

  • A larger company owning a big stake or board control.
  • Heavy economic dependence on one client/partner.
  • Shared management, owners, or facilities across “separate” firms.
  • Certain joint ventures (though SBA-compliant JVs — especially Mentor-Protégé JVs — have specific exceptions so the partners aren’t automatically affiliated for size).

Why it matters: size protests

If you win a set-aside, a competitor can file a size protest arguing you’re not actually small (often on affiliation grounds). Lose it and you lose the award. So get your size — and your affiliations — right before you certify as small, and keep documentation that supports it.

The bottom line

You’re “small” only under a specific NAICS size standard, measured on a multi-year average — and affiliation can fold other firms’ size into yours and push you over. Confirm the current standard for each solicitation’s NAICS, understand your affiliations, and don’t self-certify as small without being sure it holds up to a protest.

This article is general information, not legal advice. Size and affiliation rules are technical and change; verify the current SBA regulations or consult counsel.