A NAICS code is a six-digit number that classifies your business by the type of economic activity it performs. Federal agencies use it to publish industry statistics, the Small Business Administration uses it to decide whether your company qualifies as small, and the IRS uses it to compare your tax return against others in the same line of work. The system was built jointly by the United States, Canada, and Mexico and replaced the older Standard Industrial Classification (SIC) system in 1997.
You choose your own code. No agency assigns one to you. That choice then follows you onto tax returns, into SAM.gov, and through insurance and lending applications, so it pays to pick carefully.
What the Six Digits Mean
Each digit narrows the classification from a broad sector down to a specific national industry. The first two digits identify one of 20 major sectors, such as manufacturing (31–33) or retail trade (44–45). The third digit identifies a subsector, the fourth an industry group, and the fifth the NAICS industry. Those first five digits stay consistent across the United States, Canada, and Mexico so the three countries’ economic data can be compared.
The sixth digit is where the three countries diverge. It captures activity unique to each national market. A sixth digit of zero generally means the U.S. national industry is the same as the broader five-digit NAICS industry.
The Office of Management and Budget oversees the system and reviews it every five years. The 2022 revision collapsed several categories that had drawn a line between online and in-store sales in wholesale trade, retail trade, and information, on the theory that the distinction had lost its meaning as businesses moved to hybrid models. A narrower 2027 revision is underway, focused on new and emerging industries, especially in the bioeconomy. OMB is expected to publish final decisions during 2026, with updated codes appearing on the Census Bureau’s NAICS website in January 2027.
How to Find Your Code
The Census Bureau maintains a searchable database at census.gov/naics. Type a keyword describing what you do — “landscaping,” “software development” — and drill down through the hierarchy until you reach the six-digit code that best matches your primary activity.
The key word is “primary.” Your code should reflect whichever activity generates the largest share of your total revenue, not every service you happen to offer. A company earning 60% of its revenue from IT consulting and 40% from software licensing classifies under IT consulting. The IRS instructions for Schedule C say this plainly: pick the code that identifies “the principal source of your sales or receipts.”
Businesses With Multiple Revenue Streams
If your business genuinely spans more than one industry, the SBA looks beyond revenue alone. Under 13 C.F.R. § 121.107, it considers the distribution of receipts, employees, and costs of doing business across your operations for the most recently completed fiscal year, and may also weigh factors like contract awards and patents. This matters because your primary NAICS code sets the size standard that controls your eligibility for small-business programs.
NAICS Codes and Product Service Codes Are Not the Same
If you pursue federal contracts you’ll also see Product Service Codes (PSCs). Your NAICS code classifies what kind of business you operate; a PSC classifies what the government is buying. A widget manufacturer has a manufacturing NAICS code, and the widgets themselves fall under a PSC. Both appear in federal procurement, but the NAICS code is the one that decides whether you count as a small business for a given contract.
Where You Actually Use It
You’ll enter your NAICS code yourself, in two main places.
Your Tax Return
Sole proprietors put their six-digit code on Line B of IRS Schedule C (Form 1040), choosing from the principal business activity code list in the instructions. Corporations report the same type of code on Schedule K of Form 1120. If your primary revenue source shifts, you simply update the code on your next return. There is no separate form or notification.
SAM.gov
To bid on federal contracts you must register in the System for Award Management. You enter NAICS codes under the “Goods and Services” section of your entity profile, and SAM’s checklist points registrants to the Census Bureau’s website to look them up. You can list multiple codes reflecting the range of work you’re qualified to perform, and in many cases you should. One of them has to be designated as primary. Contracting officers use your listed codes to determine whether you’re eligible for specific solicitations, so keep the profile current as your business changes.
Why It Matters
A wrong code has real financial consequences. It can lock you out of contracts you should qualify for, skew the insurance premiums you’re quoted, or send your tax return to be measured against the wrong industry.
SBA Size Standards
The SBA sets a size standard for every NAICS industry, expressed either as a maximum number of employees or a cap on average annual receipts. Fall below the threshold and you qualify as small for federal programs, set-aside contracts, and certain loans and grants. Exceed it and you don’t, no matter how small you feel next to the giants in your field.
The thresholds vary dramatically. A new single-family housing contractor qualifies as small with up to $45 million in annual receipts. A soybean farm hits the ceiling at $2.25 million. In manufacturing, the employee threshold runs from 500 to 1,500 depending on the subsector. Pick the wrong code and you’ll be measured against a size standard that doesn’t fit your actual business.
IRS Industry Comparisons
The IRS groups returns by principal business activity code and compares reported income and expenses against norms for similar businesses. A restaurant reporting unusually low food costs against its revenue stands out from the averages for its NAICS group, and that comparison feeds into the IRS’s process for selecting returns to review. There is no specific penalty for the wrong code, but misclassification means your return gets compared to the wrong benchmarks, which can either draw unwanted attention or mask a real anomaly.
Insurance and Lending
Workers’ compensation insurers assign your business to a classification that sets your base premium rate, reflecting the expected injury costs for similar work. A roofing company pays a very different rate than an accounting firm. If your NAICS code doesn’t match what you actually do, the initial classification can be wrong, leading to premiums that are too high or too low, with the low side creating problems at audit time. Commercial lenders also request your NAICS code during loan applications to assess industry-specific risk.
Veteran-Owned Certification
Service-Disabled Veteran-Owned Small Business (SDVOSB) certification moved from the Department of Veterans Affairs to the SBA effective January 1, 2023. The SBA’s Veteran Small Business Certification Program handles verification, and your NAICS code is part of that process because it determines which size standard applies and whether you qualify as small for set-aside and sole-source contracts reserved for SDVOSBs.
Appealing the NAICS Code on a Federal Solicitation
Every federal solicitation lists a NAICS code and its associated size standard. If the wrong code is assigned, it can change which businesses qualify as small for that procurement and shut out firms that would otherwise be eligible.
Any party adversely affected by the contracting officer’s designation can appeal to the SBA’s Office of Hearings and Appeals (OHA). The appeal has to be filed within 10 calendar days after the solicitation, or an amendment affecting the code, is issued. OHA will dismiss a late appeal without considering the merits. The SBA itself can file a NAICS code appeal at any time before offers are due, but everyone else faces the 10-day window.
The appeal must be in writing and include the solicitation or contract number, the contracting officer’s contact information, and a detailed explanation of why the designation is wrong. It has to be served on both the contracting officer and SBA’s Office of General Counsel. Once it’s filed, the contracting officer stays the deadline for offers and notifies the public that an appeal is pending. One limit worth knowing: for sole-source contracts under the 8(a) program, only SBA’s Associate Administrator for Business Development can appeal. Individual businesses cannot.