NAICS Codes for Government Contracting — A Complete Guide

NAICS stands for North American Industry Classification System. It's a standardized system of numeric codes used by the U.S. federal government to classify businesses by the type of economic activity they perform. NAICS codes were adopted by the federal government in 1997, replacing the older SIC (Standard Industrial Classification) system.

Every business registered in SAM.gov must select one or more NAICS codes. These codes appear on federal contracts to describe what type of service or product is being procured. When a contracting officer posts a solicitation, they assign a NAICS code to indicate the kind of business they're looking for.

NAICS codes are structured hierarchically. A 2-digit code identifies a broad sector (e.g., 54 = Professional, Scientific, and Technical Services). A 4-digit code narrows to an industry group. A 6-digit code identifies a specific industry. Federal contracts always use 6-digit codes.

NAICS codes are central to the federal small business set-aside system. Each NAICS code has a size standard — a maximum number of employees or annual revenue — that determines whether a company is considered "small" for that code. If you qualify as small under the assigned NAICS code, you're eligible to bid on set-aside solicitations restricted to small businesses.

The set-aside programs tied to NAICS codes include: Small Business (SB) set-asides, which require "small" status under the NAICS size standard; 8(a) Business Development, for economically and socially disadvantaged small businesses; HUBZone, for businesses in historically underutilized zones; Service-Disabled Veteran-Owned (SDVOSB); and Women-Owned Small Business (WOSB).

• Each NAICS code has a unique size standard (employees or revenue)
• Size standards range from $4M to $47M in revenue, or 100 to 1,500 employees
• You can have different size status under different NAICS codes
• Self-certification is standard; SBA can verify on request
• Set-aside eligibility is determined at time of offer, not registration
• Using the wrong NAICS code can disqualify you from set-asides

While there are thousands of NAICS codes, a relatively small set accounts for the majority of federal contracting activity. IT services, professional services, construction, and logistics dominate the federal market.

Common IT NAICS codes include: 541512 (Computer Systems Design Services), 541511 (Custom Computer Programming Services), 541519 (Other Computer Related Services), 541715 (Research and Development in Physical, Engineering, and Life Sciences), and 518210 (Data Processing, Hosting, and Related Services).

Common professional services codes: 541611 (Management Consulting Services), 541612 (Human Resources Consulting Services), 541690 (Other Scientific and Technical Consulting), 561110 (Office Administrative Services), and 541910 (Marketing Research and Public Opinion Polling).

Defense and security codes include: 541330 (Engineering Services), 561210 (Facilities Support Services), 238210 (Electrical Contractors), and 488190 (Other Support Activities for Air Transportation).

Choosing the right NAICS codes starts with honestly assessing what your company does and what it has successfully delivered in the past. Don't claim codes for capabilities you don't have — agencies and prime contractors will verify your experience during proposal evaluations.

A practical approach: start with the primary service your company delivers and find the matching 6-digit NAICS code. Then expand to adjacent codes for related services you also provide. Review your historical projects and match each one to the NAICS code that best describes the work.

Look up your selected codes in the SBA size standards table to verify your eligibility. The SBA maintains a searchable size standards table at sba.gov. You want codes where you currently qualify as small — that's where the set-aside opportunities are.

• List all services you currently deliver to clients
• Match each service to the most specific NAICS code available
• Check the SBA size standard for each code
• Register all qualifying codes in your SAM.gov profile
• Research which codes federal agencies award most frequently in your space
• Review NAICS codes on contracts you've performed in the past
• Monitor adjacent codes where agencies sometimes classify similar work
• Update your codes annually as your capabilities evolve

BidLumen's onboarding process captures your company's NAICS codes as part of the initial profile setup. These codes are then used as the primary filter when ingesting federal opportunities from SAM.gov — BidLumen monitors all NAICS codes used in federal contracting and pulls every solicitation that matches your profile.

The AI scoring engine uses your NAICS codes as a strong positive signal when ranking opportunities. An opportunity with an exact NAICS code match to your primary capability will score higher than one in an adjacent code — all else being equal.

BidLumen also surfaces set-aside opportunities that match both your NAICS codes and your small business certifications, so you never miss a solicitation you're specifically qualified for. As new opportunities are posted and analyzed, they're automatically added to your Bid Insights feed ranked by relevance. See how BidLumen analyzes SAM.gov opportunities.