A system used by the US federal government to classify business revenues. Filing parties must include NAICS codes to identify types of revenue and potential competitive overlaps when making filings under the Hart-Scott-Rodino Act (HSR Act). NAICS codes are listed on the Census Bureau's website.

For more information on how the antitrust agencies use NAICS codes, see Practice Note, HSR Form: Item 5: Practical Uses of Item 5 of the HSR Form.