Your NAICS code is how the government classifies your business — get it right
The North American Industry Classification System (NAICS) assigns a six-digit code to every type of business activity. The federal government uses these codes for everything: collecting economic statistics, determining small business size standards, categorizing contract solicitations, and deciding which businesses are eligible to compete for specific opportunities.
When an agency posts a contract on SAM.gov, it assigns a NAICS code to that solicitation. Businesses registered in SAM.gov with that NAICS code are the intended audience. If your business is not registered with the relevant code, you may still technically be eligible to bid — but you will not appear in searches agencies run when looking for qualified small businesses, and your size status may not be calculated correctly for that contract category.
Getting your NAICS code right is not a bureaucratic detail. It directly affects which contracts you can find, whether you qualify as small in a given competition, and which set-aside programs you can access. Use the Contract Finder to see how contracts in your industry are categorized before you finalize your registration.
How NAICS codes are structured
NAICS codes are hierarchical. The first two digits identify the sector. Each additional digit narrows the classification until you reach the full six-digit code that identifies a very specific industry. For example: 23 is Construction (the sector), 236 is Construction of Buildings (the subsector), 2362 is Nonresidential Building Construction (the industry group), and 236220 is Commercial and Institutional Building Construction — the full six-digit code used on federal contracts.
There are over 1,000 six-digit NAICS codes covering every imaginable business activity. Most businesses have one primary code and several secondary codes that describe additional services they offer. The code used on a specific solicitation determines the size standard that applies and which businesses are evaluated as small for that competition.
How to find your NAICS code
The official NAICS lookup tool is at census.gov/naics. Search by keyword — type in what your business does and it returns matching codes with full descriptions. Read the descriptions carefully, not just the titles. Two codes can have similar titles but describe fundamentally different activities, and using the wrong one can cause your proposals to be evaluated under incorrect size standards.
A practical supplement: find businesses similar to yours that already do government contracting and look at the NAICS codes on contracts they have won. You can search USASpending.gov by company name to see their award history and the associated NAICS codes. This tells you how the government actually classifies businesses doing work similar to yours — which is more useful than trying to interpret code descriptions in isolation.
Small business size standards vary by NAICS code
This is the part most new contractors miss entirely. Being a small business is not a single universal threshold — it is determined separately for every NAICS code. The SBA sets a size standard for each code, expressed either as maximum annual average revenue or maximum number of employees over a three-year period. A company that qualifies as small under one NAICS code may not qualify as small under another.
Some examples: NAICS 561720 (Janitorial Services) has a small business size standard of $22 million in annual revenue. NAICS 541511 (Custom Computer Programming) is $34 million. NAICS 236220 (Commercial Construction) is $45 million. NAICS 336411 (Aircraft Manufacturing) is based on employee count — 1,500 or fewer employees. Your size is calculated as an average of the past three fiscal years of revenue or employment, depending on which measure applies to your code.
Check your size standard at sba.gov/size-standards before certifying your business as small on any contract. Misrepresenting your size status on a federal solicitation or in SAM.gov is a federal crime with serious consequences — do not assume you qualify without verifying.
You can and should register multiple NAICS codes
SAM.gov allows you to designate one primary NAICS code and an unlimited number of additional codes. Add every code that honestly describes work your business performs. A construction company that also provides facility maintenance, painting, and HVAC services should register all of those codes, not just the primary construction code. Each additional code opens additional solicitations where your business can appropriately compete.
Your size status is calculated independently for each NAICS code. You might be small under your primary code but exceed the size standard under a secondary one. This matters when you self-certify as small on a specific solicitation — you certify based on the NAICS code assigned to that contract, not your primary registration code.
What happens if you use the wrong NAICS code
If you bid on a contract and your business does not perform the primary activity described by that contract is NAICS code, you risk a size protest from a competitor or an eligibility challenge from the contracting officer. Size protests are adjudicated by the SBA Office of Hearings and Appeals and can result in your bid being disqualified even after a conditional award. The reputational damage with that contracting office can outlast the specific protest.
Use codes accurately. If you are genuinely uncertain whether a particular code applies to your business, consult a PTAC advisor (free) before registering — they deal with this question daily and can give you a definitive answer quickly.
Start searching with your codes in mind
Once you know your NAICS codes, use them to focus your opportunity search. The Hidden Handbook Contract Finder lets you search by industry keyword and state — our search maps plain-English terms to the relevant NAICS categories automatically, so you see solicitations that match your business without needing to memorize six-digit codes. When you find a solicitation worth pursuing, check its assigned NAICS code against your SAM.gov registration to confirm you are properly classified before you invest time in a proposal.