What is an IRS principal business code?
An IRS principal business activity code is a six-digit number that the taxpayer selects to best describe the business’s principal activity, typically the one that produces the principal source of income or receipts. It classifies the types of services and products your company offers, the industry in which the business operates and the primary consumer market that purchases from the business.
The IRS principal business code is part of the North American Industry Classification System (NAICS). The IRS uses this code to classify your business based on its principal activity, usually the one that best describes how the business earns most of its income.
The PBC is derived from the business activity that yields the highest percentage of production costs and investment in capital goods and not necessarily what occupies the most time or personnel. However, in many cases, both revenue and employment share determine a company’s business code.
“Many industry-specific tax credits, such as research and development (R&D) credits and manufacturing deductions, are PBC dependent. Choosing the wrong code may exclude your business from potential benefits.”
—Tarik Griffith, accountant
Purposes of a principal business code
The IRS and the Census Bureau use your principal business code for statistical information and to compare year-to-year revenue and other figures you report as part of your general commercial regulatory compliance.
When you grow your business, the United States Census Bureau uses your PBC to collect, analyze and publish statistics related to the U.S. economy. Additionally, the Small Business Administration connects the principal business code of your business’s industry to the size of your business. This helps distinguish small to medium companies from large corporations.
Organizations use these business activity codes to file their tax returns with the IRS and apply for tax incentives, grants and loans with the U.S. Small Business Administration. Principal business codes are also created and used for certain other business identification purposes with the U.S. government. The principal business code for taxes is also sometimes called the professional activity code.
Where to find the code
Principal business codes are organized by industry groupings, and can be found in the instructions for the IRS Schedule C form. Sole proprietorships or single-member limited liability companies (LLCs) use this form to report their profits and losses.
These business code Schedule C listings are also available on other business-related tax forms and information sheets. Another place to find them is the North American Industry Classification System website, which offers a searchable interface to locate IRS business activity codes.
Detailed explanation of the principal business code
The IRS business codes identify how the IRS classifies businesses and business activity. The first two digits classify a company based on the broad category it’s principally involved in.
For example, businesses mainly operating in the broadly defined areas of fishing, hunting, agriculture, forestry, animal husbandry and all supporting industries start with an 11 as their first two digits. Companies working mainly in the construction and civil engineering industries have IRS business activity codes that start with 23.
Within each of these broad industry categories are multiple smaller market niches for certain aspects of each industry. You can reference these for your company’s main activity to find its complete IRS principal business code.
For another example, one subcategory under the general category of construction-related codes starting with 23 is Residential Building Construction, which is coded as 236110. If your business generates most of its labor and revenue from apartment building construction, this code will apply to its tax filings.
A category for “All Other” and another for “All Other Personal Services” also exist. Both can be used as general business activity codes for IRS categories for companies whose activities don’t clearly fit into any of the major industry-specific business code areas.
Use the “All Other” category sparingly. Overuse of catch-all codes for companies can lead to increased audit scrutiny if financials do not align with market peers.
Government agencies such as the Social Security Administration, Census Bureau and Internal Revenue Service often assign their business activity codes based on the information they have from documents filed by your company. This means your code’s numerical sequence with the IRS may differ from documents from another agency:
| Digit sequence | Meaning |
| First 2 digits | Broad industry group (e.g. 23 = Construction) |
| 3rd digit | Subsector |
| 4th-5th digits | Industry group |
| 6th digit | National industry (specific to U.S. economy) |
To find your specific business code for taxes, use these steps:
1. Identify your primary industry through a search
NAICS is a hierarchical system with 20 sectors, and its levels narrow from sector to subsector, industry group, NAICS industry, and national industry. For example, companies in the food service, accommodation and drinking places sector would have 72 as their business code. You can also search for business code IRS classifications via the U.S. Census Bureau’s platform or the IRS itself on its list of principal business codes.
2. Determine your business’s subcategory
The North American Industry Classification System lists 96 subcategories under its 20 main categories that describe the more specific activities of companies in each primary industry. This part of the principal business code is a three-digit number that further reflects the types of business activities your organization is involved in. For example, accommodation would be a subcategory under the food, accommodation and drinking places sector.
The system contains 317 industry types that you can correlate to your business within each subcategory in the North American Industry Classification System. To determine the industry group that best fits your business’s operations and activities, identify the one that describes your primary activity. For example, in the accommodation subcategory, a hotel business might fall under the industry group of traveler accommodations.
Typically, you select the principal business code that best matches your business’s main activity. If you have multiple locations or are considering relocation, choose the code that best reflects the primary activity of the business overall. You should use only one principal business code unless the form or filing instructions specifically ask for additional codes.
Selecting the correct business code is both a compliance step and a strategic move that defines how the IRS, lenders and federal agencies regard your company. When picked correctly, it helps properly align the company and its activities.
How the principal business code applies to taxes
When you file your employer taxes, the IRS requires a principal business activity code on certain returns, including Schedule C and forms such as Form 1065 and Form 1120/1120S when requested by the form instructions. If you have a single principal business code, enter that into your tax information.
If your business falls into more than one distinct industry group, it’s important to have principal business codes to reflect that. Generally, a business is only required to record the PBC that corresponds to the business activities responsible for its primary revenue.
When you’re filling out your business tax return, you are typically required to include your principal business code, including category and subcategory, along with a brief description, which is an outline of your principal business.
Maintaining consistent codes can prevent audits, speed up the processing of SBA applications and help secure certain tax credits and deductions. Verifying matched codes can prevent IRS correspondence or a delayed application process.
Selecting the right IRS Principal Business Code can be vital for accurate tax classification, compliance and unlocking industry-specific benefits and credits. The correct PBC helps verify proper alignment with your core operations, helping avoid audits while supporting eligibility for government programs and incentives.
