Adding a NAICS code to your LLC isn’t one task — it’s a handful of separate filings, and which one you need depends on why the code is being asked for. Here is how to add a NAICS code to your LLC in each place it actually shows up: the IRS forms tied to your EIN and tax return, your state’s formation or amendment paperwork (only in eight states), and your SAM.gov registration if you plan to bid on federal contracts. Your LLC doesn’t hold a single permanent NAICS code the way it holds an EIN; you report the code on the filing that needs it, and you update it there when things change.
Find the Right Code First
Before you add a code anywhere, look it up on the Census Bureau’s official NAICS search tool at census.gov/naics, which lets you search by keyword or browse the full list.1U.S. Census Bureau. North American Industry Classification System – NAICS Search by what your business actually does — the goods you sell or services you provide — not by your legal structure. “Residential cleaning services” returns something useful; “LLC” does not.
The code is six digits, with each digit narrowing the classification from broad economic sector down to a specific national industry.2United States Census Bureau. Economic Census: NAICS Codes and Understanding Industry Classification Systems
If Your LLC Does More Than One Thing
Pick the code that matches whichever activity brings in the most money. The IRS instructions for Form 1065 spell this out: determine the code based on the activity generating the largest percentage of your total receipts.3Internal Revenue Service. 2025 Instructions for Form 1065 If your LLC earns 60% of its revenue from IT consulting and 40% from software licensing, your primary code reflects the consulting.
The Census Bureau assigns only one code per business under this primary-activity rule. SAM.gov is more flexible and lets you list a primary plus multiple secondary codes, which matters for federal contracting (covered below).4SAM.gov. Entity Registration Checklist
Adding a Code to Your EIN Application
Form SS-4, the EIN application, does not actually ask for a six-digit NAICS code. Line 16 gives broad category checkboxes (construction, retail, manufacturing, and so on), and Line 17 asks for a written description of what your business does.5Internal Revenue Service. Instructions for Form SS-4 (Rev. December 2025) The government assigns the NAICS code internally: the Social Security Administration runs your application through a coding program that matches your description to a six-digit code.6Social Security Administration. POMS: RM 01002.003 – How SSA Processes SS-4 Applications
So your Line 17 description is doing the real work. “General contractor for residential buildings” lands you in a different classification than “commercial framing subcontractor,” even though both check the construction box on Line 16. Write the description specifically, because that’s what determines the industry bucket the government puts you in.
Adding or Updating the Code on Your Tax Return
Your annual federal return is the routine place to report a NAICS-based business activity code, and it’s also the easiest way to change it if your business has shifted. You enter the code fresh each year, so if your primary revenue source has changed, you simply put the new code on that year’s return. There is no separate IRS amendment form for updating industry classification.
Where the code goes depends on how your LLC is taxed:
Multi-Member LLCs on Form 1065
Most multi-member LLCs file as partnerships. The principal business activity code goes on page 1, Item C (“Business code number”), with a business activity description in Item A and your principal product or service in Item B.7Internal Revenue Service. Form 1065 – 2025 The full code list is in the Form 1065 instructions.3Internal Revenue Service. 2025 Instructions for Form 1065
Single-Member LLCs on Schedule C
A single-member LLC that hasn’t elected corporate taxation reports on Schedule C of the owner’s Form 1040. The six-digit code goes on Line B, and the code list appears at the end of the Schedule C instructions.8Internal Revenue Service. 2024 Instructions for Schedule C
LLCs Taxed as Corporations on Form 1120
If your LLC has elected C corporation taxation, the code goes on Schedule K of Form 1120: the six-digit code on line 2a, business activity description on line 2b, and product or service description on line 2c.9Internal Revenue Service. Instructions for Form 1120
Adding a Code to State Formation Documents
Most LLC owners assume their state formation paperwork asks for a NAICS code. Most states don’t. Only eight require a NAICS code on LLC formation documents: Alaska, Arkansas, Connecticut, Georgia, Louisiana, Mississippi, New Hampshire, and New Mexico. In the other 42 states and Washington, D.C., there is no NAICS field on the Articles of Organization to add anything to.
If your LLC is formed in one of those eight states and you need to change the code after formation, you’ll typically file Articles of Amendment with the Secretary of State’s office. Many states accept online filings; some still take paper. Fees generally run in the $25 to $60 range. Online submissions tend to process within a few business days; mailed filings can take several weeks depending on the office’s backlog.
Some states also include a business activity or NAICS field on the annual or biennial report form. If yours does, that’s the easier route for an update — no amendment filing needed. Check your state business division’s website to see which forms carry the field.
Adding NAICS Codes to SAM.gov for Federal Contracts
This is where NAICS codes matter most. To bid on federal contracts, your LLC must register in the System for Award Management and list at least one NAICS code. SAM lets you designate one primary code and add multiple secondary codes to reflect your full range of services.4SAM.gov. Entity Registration Checklist The registration checklist points you to the Census Bureau’s search tool to look up the right codes before entering them.
SAM registrations must be renewed annually, and each renewal is a natural moment to add, remove, or update codes. If your LLC has expanded into new service areas, add the corresponding secondary codes so contracting officers searching SAM can find you.
Why Your SAM Codes Have to Be Right
The Small Business Administration ties its size standards directly to NAICS codes. Each code carries a maximum threshold — either annual revenue or number of employees — that determines whether your LLC qualifies as a “small business” for federal programs, and thresholds vary widely by industry.10eCFR. Part 121 Small Business Size Regulations
When a federal agency issues a solicitation, the contracting officer assigns one NAICS code and one size standard to that solicitation. Your LLC must be small under that specific code’s threshold to qualify for any small-business set-aside on the contract.10eCFR. Part 121 Small Business Size Regulations Misrepresenting size status in federal procurement can lead to suspension, debarment, civil penalties under the False Claims Act, and criminal penalties under the Small Business Act.11Federal Register. Small Business Size and Status Integrity
Why the Code You Pick Matters Beyond the Filing
The classification follows your LLC into places that affect your bottom line. Insurance carriers use industry classifications when setting commercial premiums; being coded into a higher-risk industry can mean noticeably higher rates for general liability or workers’ compensation, even if your actual operations are relatively safe. Some lenders and payment processors also flag certain NAICS codes as high-risk, which can affect loan eligibility or merchant account approval.
Any time your LLC’s primary revenue source shifts meaningfully, take a few minutes to verify the code still matches — on your next tax return, in SAM.gov if you’re registered, and with your state if it’s one of the eight that tracks it.