In almost every situation, you assign your own NAICS code. No federal office reviews your business and hands you an official classification. You look up the six-digit code that best fits what you do, and you enter it on tax returns, loan applications, and government registrations. The one meaningful exception is federal contracting: for each solicitation, the contracting officer selects the single NAICS code that applies, and that choice governs who qualifies to bid.
How You Pick Your Own Code
When you form a business, no certificate of classification arrives. You’re expected to identify the six-digit NAICS code that best matches your primary activity. The Census Bureau hosts a searchable directory at census.gov/naics where you can type keywords and drill down from broad sectors to specific industry descriptions.1U.S. Census Bureau. North American Industry Classification System (NAICS)
The selection rule is a revenue test. Figure out which single activity brings in the largest share of your annual receipts, and use the code for that activity. A company earning 60% of its income from software development and 40% from consulting classifies under a software code, not a consulting one. If your revenue mix shifts, the code shifts with it.
Getting this right matters because the code follows you. It appears on tax filings, factors into loan eligibility, and feeds insurance classifications. Nobody signs off on your choice at the front end, but several agencies rely on it later.
Who Assigns NAICS Codes on Federal Contracts
Federal procurement doesn’t leave the code to the bidder. When an agency posts a solicitation, the contracting officer picks the single NAICS code that best describes the principal purpose of what’s being acquired. Every solicitation must include exactly one NAICS code and one corresponding size standard.2eCFR. 13 CFR 121.402 – What Size Standards Are Applicable to Federal Government Contracting Programs The officer works from the industry descriptions in the NAICS Manual, the solicitation’s product or service description, and which component accounts for the greatest percentage of contract value.
The choice has real consequences. The NAICS code the contracting officer picks determines the size standard for that contract, which in turn decides whether your business counts as “small” for that particular opportunity. A code with a low size standard can lock out firms that would qualify as small under a different code covering similar work.
Appealing the Contracting Officer’s Choice
If you think a contracting officer picked the wrong code, you can appeal to the SBA’s Office of Hearings and Appeals. The deadline is strict: 10 calendar days after the solicitation is issued, or after an amendment changes the NAICS code. Miss the window and the appeal is dismissed.3eCFR. Subpart C – Rules of Practice for Appeals From Size Determinations and NAICS Code Designations
The petition has no required format, but it must include the solicitation number, the contracting officer’s contact information, and a detailed explanation of why the designation is wrong. Copies go to both the contracting officer and the SBA’s Office of General Counsel. If OHA rules in your favor, the contracting officer must amend the solicitation, and the new code applies to future solicitations for the same work. OHA decisions on NAICS appeals are final and cannot be reconsidered.3eCFR. Subpart C – Rules of Practice for Appeals From Size Determinations and NAICS Code Designations
What the Agencies Do With the Code You Assigned
No agency assigns your code, but several rely on the one you report.
Internal Revenue Service
The IRS requires a NAICS-based Principal Business Activity code on multiple return types. Corporations enter theirs on Form 1120, Schedule K, choosing the six-digit code for the activity that generates the highest percentage of total receipts.4Internal Revenue Service. Instructions for Form 1120 (2025) Sole proprietors do the same on Schedule C, Line B, from the code list printed in the instructions.5Internal Revenue Service. 2025 Instructions for Schedule C (Form 1040) The IRS compares your return against statistical norms for other businesses using the same code, and significant divergence from industry averages can factor into audit selection.6Internal Revenue Service. IRS Audits
Small Business Administration
The SBA uses NAICS codes as the backbone of its size standards. Whether your business qualifies as small depends on the standard tied to your specific code. The SBA measures business size mainly by average annual receipts or average number of employees. For receipts-based industries outside agriculture, current thresholds run from $8 million to $47 million. Agricultural industries range from $2.25 million to $5.5 million.7Federal Register. Small Business Size Standards: Monetary-Based Industry Size Standards A handful of financial industries use asset-based thresholds instead. Qualifying as small under the right code opens the door to set-aside contracts and SBA loan programs.8U.S. Small Business Administration. Table of Size Standards
Bureau of Labor Statistics
The BLS uses NAICS codes in the Quarterly Census of Employment and Wages to track employment and wages by industry. QCEW data serves as the benchmark for other major BLS programs and feeds the Bureau of Economic Analysis’s personal income calculations.9U.S. Bureau of Labor Statistics. QCEW Overview Your code decides which industry bucket your payroll data lands in.
The Census Bureau’s Role
The Census Bureau maintains the NAICS system under the direction of the Office of Management and Budget, but it does not assign codes to individual businesses. During each Economic Census, conducted every five years, the Bureau sends questionnaires to millions of business locations and may internally reclassify an establishment based on the responses. That internal reclassification feeds benchmark economic reports; it does not override the code you use on your tax return or SAM.gov profile.
Changing the Code You Assigned Yourself
On tax filings, the update is simple. Enter the new code on your next return. Corporations change the Principal Business Activity code on Form 1120, Schedule K. Sole proprietors put the new code on Schedule C, Line B.5Internal Revenue Service. 2025 Instructions for Schedule C (Form 1040) There’s no separate petition or form. The new code takes effect for that tax year and carries forward.
Government contractors manage their codes through the System for Award Management. You update NAICS codes by editing your entity registration, which you must renew every 365 days to keep active.10SAM.gov. Entity Registration Updates can take up to 10 business days to process. Because your SAM.gov profile controls which contracts you’re eligible to bid on, an outdated profile can mean missed opportunities or eligibility questions during award.
What Happens if You Assign the Wrong Code
An honest mistake is usually fixable by entering the right code on your next filing. The IRS peer-comparison problem is the quiet cost of getting it wrong: a restaurant filed under a consulting code will show cost-of-goods and payroll ratios that look strange for consulting, which can invite scrutiny that a correct code would have avoided.6Internal Revenue Service. IRS Audits
Deliberate misrepresentation is a different matter, especially in federal contracting. Businesses that falsely claim small business status by manipulating their NAICS code to qualify for set-asides face exposure under the False Claims Act. The statute sets penalties at $5,000 to $10,000 per false claim; after inflation adjustments those figures currently sit between $14,308 and $28,619 per violation, plus triple the damages the government sustained.11Office of the Law Revision Counsel. 31 USC 3729 – False Claims Criminal prosecution is also possible; the SBA’s Office of Inspector General investigates firms that misrepresent eligibility for programs like 8(a), HUBZone, and service-disabled veteran-owned set-asides.