NAICS Codes for Government Contracting: How to Choose Yours (2026 Guide)

Ask any experienced government contractor what a new business should figure out first, and most will give you the same unglamorous answer: your NAICS codes. Those six digits decide which contracts you're eligible to win as a small business, which set-asides you qualify for, and — just as important — whether contracting officers can find you at all when they go looking for vendors. Pick well and you compete in a lane sized for businesses like yours. Pick badly and you either drown in irrelevant solicitations or get disqualified from work you could have won.

This guide explains what NAICS codes actually are, how the 6-digit hierarchy works, how to choose your primary and secondary codes, why the same revenue can make you "small" under one code and large under another, and how to use NAICS filters to find the government bids that fit your business.

What a NAICS code is — and why it decides which contracts you can win

NAICS (pronounced "nakes") stands for the North American Industry Classification System. It's a standardized numbering scheme, maintained by the U.S. Census Bureau and revised every five years, that assigns every industry in the economy a six-digit code. Plumbing contractors are 238220. Janitorial services are 561720. IT consultants writing custom software are 541511. The government didn't invent NAICS for procurement — it's a statistical tool — but federal, state, and many local agencies have adopted it as the common language for describing what they're buying and who sells it.

For contractors, three things flow directly from those six digits:

• Small-business size standards. The Small Business Administration attaches a size standard — a revenue ceiling or an employee-count ceiling — to every NAICS code. Whether your company counts as "small" is always answered relative to a specific code, never in the abstract.
• Set-aside eligibility. Roughly a quarter of federal contract dollars are reserved for small businesses, plus additional set-asides for 8(a), HUBZone, women-owned, and service-disabled-veteran-owned firms. When a contracting officer sets a contract aside, eligibility is judged against the size standard of the NAICS code assigned to that solicitation. The code literally gates who may compete.
• How agencies find you. When buyers do market research — searching SAM.gov's vendor database or the SBA's Dynamic Small Business Search for firms that can do the work — they search by NAICS code. If a code isn't in your registration, you're invisible in that search, no matter how qualified you are.

In short: NAICS codes determine what you can bid on as a small business, and whether the government even knows you exist. That's why choosing them deserves more than the thirty seconds most businesses spend on it during SAM.gov registration.

How the 6-digit hierarchy works

NAICS codes aren't arbitrary numbers — each digit narrows the classification. Reading left to right, a code moves from a broad sector of the economy down to a specific industry. Here's the full path for one of the most common codes in government IT contracting, 541512 — Computer Systems Design Services:

Notice how much the last digit matters. 541511 (custom computer programming) and 541512 (systems design and integration) sit one digit apart and describe overlapping-sounding work, but contracting officers treat them as distinct industries — and historically they've even carried different size-standard treatments. The same pattern repeats across construction (236xxx vs. 238xxx trade contractors), logistics, professional services, and manufacturing. When you evaluate a code, always read the official definition at the full six-digit level, including the "illustrative examples" and cross-references the Census Bureau publishes, rather than going by the title alone.

How to find your primary NAICS code

Your primary code should describe the activity that generates the largest share of your revenue — not the work you aspire to, and not the broadest umbrella you can stretch over everything you do. Three practical ways to zero in on it:

1. Use the official Census lookup

The Census Bureau's NAICS search at census.gov/naics lets you type keywords ("electrical contractor," "IT support," "janitorial") and browse matching codes with full definitions and examples. Read two or three candidate definitions side by side; the right one usually becomes obvious once you see what each explicitly includes and excludes.

2. Look at what incumbents and competitors use

This is the step most businesses skip, and it's the most valuable. Look up recent contract awards for the kind of work you actually want — on USAspending.gov, in SAM.gov award notices, or in the solicitations themselves — and note which NAICS code the agency assigned. If the contracts you want to win are consistently solicited under 561210 and you registered under something adjacent, you're fishing in the wrong pond. Your codes should match the codes buyers use for your kind of work, because the buyer's choice is the one that counts.

3. Sanity-check against your revenue

If an auditor looked at last year's invoices, which activity would account for the biggest share? That's your primary code. This matters because your primary NAICS is what shows first in vendor searches and what programs like 8(a) evaluate your business against.

Primary vs. secondary codes: register more than one

SAM.gov asks for one primary code but lets you add secondary codes — and you should. Most real businesses do more than one thing: an IT firm might design systems (541512), write custom software (541511), resell hardware (423430), and provide support services (541519). Each of those is a separate stream of solicitations, and each secondary code you register makes you findable to buyers searching that category.

How many is sensible? Three to eight covers most small businesses. Two rules keep you honest:

• Only list codes you can genuinely perform today. A contracting officer who sees a five-person consultancy registered under thirty codes spanning construction, catering, and cybersecurity concludes the firm doesn't know what it does. Codes are a credibility signal, not a lottery ticket.
• Add a code when you start pursuing that work, not after. If you're expanding into a new service line, register the code as soon as you can credibly deliver — being searchable precedes being awarded.

One clarification that trips up newcomers: for most solicitations you can bid under a code you haven't registered, as long as you can do the work and meet the size standard. Registered codes mainly control discoverability and program eligibility reviews. But since adding a code is free and takes minutes, there's rarely a reason to bid regularly under an unregistered one.

Size standards: why the same revenue is "small" in one code and large in another

Here's the part of NAICS that directly changes what you're allowed to win. The SBA publishes a size standards table assigning every code either a revenue ceiling (average annual receipts over five years) or an employee ceiling. The ceilings vary enormously by industry, because a "small" manufacturer and a "small" janitorial firm are very different animals:

• Many professional-services codes (including 541512) carry revenue ceilings in the low tens of millions of dollars.
• General construction codes (236xxx) run several times higher, reflecting the pass-through cost of materials and subcontractors.
• Most manufacturing and wholesale codes use employee counts instead — commonly 500 to 1,500 employees — so a hardware reseller with $80M in revenue and 40 employees can still be "small."

The consequence: a company with $25M in average receipts might be comfortably small under a construction code, right at the line under a services code, and "other than small" under another services code with a lower ceiling. Small is never a property of your business — it's a property of your business under a specific code. Two practical takeaways:

1. Check the size standard on every set-aside before you bid. The solicitation states its assigned NAICS code and size standard. Your eligibility is judged against that code — not your primary, not your favorite.
2. Factor size standards into code selection. When two codes legitimately describe your work, the one with the higher ceiling keeps you eligible for set-asides longer as you grow. That's not gaming the system — the SBA expects you to pick the accurate code, but where definitions genuinely overlap, the choice is yours to make deliberately.

Common NAICS mistakes that cost contractors money

• Picking a code that's too broad. Registering under a catch-all like generic "consulting" because it feels safe means your vendor profile matches nothing specific, and the bids solicited under precise codes never surface in your searches. Specific codes win; vague codes vanish.
• Mismatching code and capability. Choosing a code because it has an attractive size standard or lots of set-asides, when your past performance tells a different story, backfires the moment a contracting officer or SBA size protest examines the gap. Your codes, your capability statement, and your award history should tell one consistent story.
• Never updating your codes. Businesses evolve; registrations fossilize. The reseller that became a managed-services firm three years ago but still lists only distribution codes is invisible for every services opportunity. Review your codes at least annually and at every SAM.gov renewal — and remember the whole system gets revised every five years (the 2022 revision renumbered several industries; the next revision cycle is due in 2027), so codes can change under your feet.
• Ignoring the solicitation's assigned code. Your registration doesn't decide set-aside eligibility — the code the contracting officer put on the solicitation does. Bidding a set-aside where you exceed that code's size standard wastes a proposal and can trigger a protest.

Using NAICS codes to find bids — and stop drowning in noise

Beyond eligibility, NAICS codes are the single best filter for finding opportunities. Federal solicitations carry an assigned NAICS code, and most state and local systems either use NAICS or map to it. Filtering a bid search by your handful of codes cuts millions of open solicitations down to the slice that's actually addressed to businesses like yours — it's the difference between reading two hundred irrelevant listings a day and five relevant ones.

A workable routine looks like this: search by your three to eight codes, layered with the geography you can serve — say Texas or California if you're regional — and the solicitation types you respond to, like RFPs. (If the RFP/RFQ/RFI alphabet is still fuzzy, our guide to RFQs, RFPs, and RFIs untangles it.) Then automate it: response windows on government bids are often just two to four weeks, so the businesses that win are the ones notified the day a matching bid posts, not the ones who stumble on it a week later. Our companion guide on how to find government bids covers that whole system end to end.

Frequently asked questions

How many NAICS codes can my business have?

There's no legal limit. You designate one primary code in SAM.gov and can add as many secondary codes as genuinely describe work you can perform. In practice, most small contractors list between three and eight. Listing dozens of unrelated codes doesn't expand your reach — it signals to contracting officers that you don't know what you do.

Who assigns my NAICS code — the government or me?

You choose your own codes when you register in SAM.gov; nobody assigns them to you. However, the contracting officer assigns a single NAICS code to each solicitation, and that code — with its size standard — governs who qualifies as small for that specific contract, regardless of what you registered.

Can I bid on a contract under a NAICS code I haven't registered?

Generally yes. Registered codes are primarily a discoverability and matching tool; most solicitations don't require the assigned code to appear in your SAM.gov profile. What matters is that you can actually perform the work and, on set-asides, that you meet the size standard of the solicitation's code. Still, register any code you bid under routinely — it's free and it makes agencies able to find you.

What happens if my company outgrows a size standard?

You become "other than small" for that code and lose set-aside eligibility under it — but only under that code. Because ceilings vary by industry, the same revenue can leave you small under one NAICS and large under another. Revenue-based size is measured as average annual receipts over five years, so growth phases in gradually rather than overnight.

The bottom line

NAICS codes look like bureaucratic trivia, but they're the addressing system of government procurement: they decide which set-asides you qualify for, whether the SBA considers you small, whether buyers can find you, and which solicitations reach your inbox. Spend an afternoon getting them right — verify your primary code against the Census definitions and against the codes on contracts you want, register the secondary codes you can genuinely perform, note the size standard attached to each, and revisit the whole list annually. Then put those codes to work as search filters, so the right opportunities find you on day one of every response window.