NAICS codes are the six-digit classifications the federal government uses to describe what a business does. They sit underneath almost everything in federal contracting: how opportunities are categorized, whether you count as “small,” and which set-asides you can pursue. Getting them right matters.

What a NAICS code is

NAICS stands for the North American Industry Classification System. Each six-digit code identifies a specific industry — for example, a code for “Custom Computer Programming Services” or “Janitorial Services.” When an agency posts a solicitation, it assigns a NAICS code that signals the kind of work and the size standard that applies.

Your business can have many NAICS codes (you’ll list them in SAM.gov), but one is designated your primary code.

Why the primary code matters

Your primary NAICS code is the one that best represents your main line of business. It carries weight because:

  • It signals your core capability to agencies and to matchmaking/search systems.
  • It’s tied to your size standard — and for the 8(a) program and similar contexts, your primary code helps frame how SBA views your firm.

Choosing a primary code that doesn’t reflect what you actually do (or sell most of) can misclassify you and steer the wrong opportunities your way.

Size standards attach to NAICS codes

Here’s the part that surprises people: “small business” is defined per NAICS code, not once for your whole company. Each code has a size standard set by the SBA — either a revenue cap (average annual receipts, e.g. $X million) or an employee-count cap, depending on the industry.

That means you can be “small” under one code and “other than small” under another. When you bid a solicitation, what matters is whether you’re small under that solicitation’s NAICS code. Always check the size standard for the specific code on the opportunity.

How to choose your codes

  1. Start from what you actually deliver. Look up the codes that match your real services or products in the NAICS manual.
  2. Pick the primary that reflects your main revenue line. Not your aspiration — your core.
  3. Add the secondary codes you can credibly perform. They broaden the opportunities you’ll be matched to, but don’t pad the list with work you can’t deliver.
  4. Check each code’s size standard. Confirm you’re small where it counts, and note the codes where you’re near the threshold.
  5. Revisit periodically. As your business shifts, your primary code may need to change.

How it ties into strategy

  • Opportunity matching and search tools key heavily off NAICS — the right codes mean better-fit opportunities surface to you.
  • Set-aside eligibility runs through size standards, which run through NAICS. See the set-aside overview.
  • If you’re approaching a size-standard ceiling under your primary code, that’s a strategic signal about which work to pursue (and when teaming or graduating off a program makes sense).

The bottom line

Treat NAICS codes as a deliberate choice, not a form field. Your primary code shapes how the government sees you and which opportunities you’re matched to; the size standards behind each code determine where you compete as a small business.

This article is general information, not legal advice. NAICS codes and SBA size standards are updated periodically; verify the current code and size standard on sam.gov and the SBA size-standards table.