You can find your company’s NAICS code for free in two places. If you’ve filed a federal tax return, the six-digit code is already printed on it. If you haven’t, or you need a fresh classification, the U.S. Census Bureau runs a free keyword search at census.gov/naics that walks you through the current list.
Pull Your Most Recent Tax Return
This is the fastest route. Corporations report the code on Form 1120, Schedule K, lines 2a through 2c, which ask for the six-digit code, a description of the business activity, and the product or service generating the most revenue.1Internal Revenue Service. Instructions for Form 1120 (2025) Sole proprietors enter the same information on Line B of Schedule C (Form 1040).2Internal Revenue Service. Instructions for Schedule C (Form 1040) (2025) Partnerships use Form 1065 and S corporations use Form 1120-S, both with similar fields.
One caveat. The IRS labels these “principal business or professional activity codes” rather than NAICS codes. The six-digit codes on tax forms are drawn from the NAICS system, but the IRS publishes a condensed version of the full Census Bureau catalog.2Internal Revenue Service. Instructions for Schedule C (Form 1040) (2025) For most businesses the code will match in both places. If you operate in a niche or hybrid field, the Census Bureau’s full list may offer a more specific match than the IRS chart.
Search the Census Bureau’s Free Tool
The Census Bureau maintains the official NAICS lookup at census.gov/naics, and it costs nothing to use.3Census Bureau. North American Industry Classification System (NAICS) The current version is 2022 NAICS, so choose that search when the tool asks. Type a few concrete words that describe what your business actually does. Think “residential roofing,” “pet grooming,” or “machine shop.” The tool returns a list of candidate codes with their descriptions.
Don’t grab the first result. Read the full description for each candidate and pick the code whose description best matches the activity that generates the largest share of your revenue, not the activity you find most interesting or hope to grow into. A shop that manufactures custom furniture and also sells it retail uses the manufacturing code if manufacturing brings in more money. A shop that mostly resells furniture built by others uses the retail code.
Understand the Six-Digit Structure
NAICS codes are built in layers, and knowing the structure makes the search much easier. Each layer adds specificity:4United States Census Bureau. Economic Census: NAICS Codes and Understanding Industry Classification Systems
- Two-digit sector: the broadest grouping (23 = Construction).
- Three-digit subsector: narrows the category (238 = Specialty Trade Contractors).
- Four-digit industry group: more specific still (2381 = Foundation, Structure, and Building Exterior Contractors).
- Five-digit NAICS industry: shared across the U.S., Canada, and Mexico (23811 = Poured Concrete Foundation and Structure Contractors).
- Six-digit national industry: the most detailed U.S.-specific classification.
If the search tool gives you too many results, identify your two-digit sector first and drill down. Too few results? Broaden the keywords. The goal is a six-digit code that precisely describes your primary revenue-generating activity.
What to Do If Your Business Does Several Things
Plenty of companies do more than one thing. A single business might manufacture, sell online, and install what it sells. The Census Bureau assigns one NAICS code per establishment based on the primary activity, generally the one that generates the most revenue. That’s the code you report on your tax return.
Other systems handle multiple activities differently. The System for Award Management (SAM.gov), where businesses register for federal contracting, lets you list several NAICS codes, and each carries its own SBA size standard. Listing secondary codes for legitimate lines of business helps you qualify for contracts in more than one category. Insurance carriers sometimes track secondary codes as well to price coverage accurately.
If your revenue mix shifts and a different activity becomes the top earner, your primary NAICS code should change to match. There’s no IRS form dedicated to a NAICS code change; the update happens when you file your next return with the new code. If your state business registration lists an industry classification, you may need to file an amendment with the state too.
Email the Census Bureau for Help
When the search tool doesn’t produce a clear match, which happens more often with hybrid businesses and emerging industries, you can email the Census Bureau directly at NAICS@census.gov for classification guidance.5Census Bureau. Subject/Topic Contacts Include your name, a phone number, and a detailed description of what your business does, what it sells, and how the products or services are produced. The more specific you are, the better the recommendation.
The Census Bureau won’t issue a formal certificate or a binding classification. What you get is a recommendation from the people who maintain the system, and it carries weight if questions come up during an audit or a government contract review.
Keep Your Code Current
The NAICS system is revised every five years to capture new and evolving industries. The current codes come from the 2022 revision, and the next update, 2027 NAICS, is scheduled for release in January 2027.6U.S. Census Bureau. NAICS Update Process Fact Sheet If your business operates in a field that has changed significantly since 2022, the 2027 revision may introduce a code that fits better than any current option.
Between revisions, revisit your code whenever your primary revenue source changes. A web design firm that gradually shifts to mostly selling software subscriptions has moved industries for classification purposes. The code on next year’s return should reflect what you do now, not what you did when you first filed. There’s no penalty for updating to a more accurate code. Sticking with the wrong one can skew IRS industry benchmarks that draw audit attention and can cost you eligibility for SBA programs and government contracts tied to the correct classification.