Your Schedule C business code is the six-digit code that best describes your principal business activity. Enter it on line B using the activity list in the instructions for the tax year being filed. The IRS directs filers to choose the activity identifying the principal source of their sales or receipts. [1]
Start with what the business actually earns money doing
Write a plain-language description before searching for a code. “I design websites for clients” is more useful than “I have an online business.” The delivery channel, legal name, and software you use do not necessarily identify the underlying activity.
- List the products or services that produced revenue.
- Identify the main activity by its sales or receipts.
- Find the closest category in the Schedule C instructions.
- Read the description beside the six-digit code.
- Save the code and a short explanation with the return records.
The IRS activity list is based on the North American Industry Classification System, or NAICS. However, the filing instructions are your starting point for the code the return requests. [1]
A business activity code is not an EIN
| Identifier | What it identifies | How it is used |
|---|---|---|
| Principal business activity code | The type of business activity | Classification on Schedule C |
| Employer identification number | A particular taxpayer entity | Business tax identification where required |
| Business name | The name under which you operate | Identifying the activity or business on records |
If you are looking for the entity’s federal tax ID rather than its activity classification, use our guide to recovering or checking an existing EIN. For changes to IRS business records, see Form 8822-B and responsible party updates.
How NAICS search can help
The Census Bureau’s official NAICS search lets you explore industry descriptions by keyword or code. Use it to understand unfamiliar categories, then confirm the choice against the IRS list for the return year. Census currently provides the 2022 system and information about proposed 2027 revisions, so a future classification proposal should not be treated as an already adopted tax-return instruction. [2]
For example, a person who makes and sells handmade furniture should first describe the production activity, products, and revenue sources. Searching only for “internet sales” could miss information needed to classify the work appropriately. This example illustrates the selection process rather than assigning a code without knowing the facts.
What if you have more than one business?
Schedule C reports income or loss from a sole proprietorship activity. Its instructions address separate businesses and the information to provide for each. Before combining unrelated work under one code, review the business structure and the instructions with the person preparing the return. [1][3]
Keep separate income and expense summaries where activities are distinct. A code selection should follow the records; it should not be used to turn personal expenses into business deductions or to choose a preferred tax result.
Final checks before filing
- Use the correct tax-year instructions.
- Check all six digits rather than relying on an autocomplete label.
- Match the description to the principal revenue activity.
- Confirm that an EIN has not been entered in the activity-code field.
- Retain the selection rationale if the business changes over time.
Use our Schedule C instructions reference when preparing the return. If the classification is still unclear, ask an eligible tax professional to evaluate the actual activities rather than selecting a generic code simply to clear a software warning.
Primary sources
Sources checked: October 31, 2026.