How we build the data

A scheduled job downloads the official files every day, checks they look complete (for example, that there are 20 NAICS sectors and about 1,012 six-digit codes), and rebuilds the site only if something changed. If a file fails a check, the site keeps the last good data.

United States

• Codes and definitions: the US Census Bureau's 2022 NAICS structure and descriptions files.
• Activities under each code: the Census 2022 NAICS index file, about 20,000 entries. The finder searches these.
• Size limits: SBA's table of small business size standards, effective March 17, 2023, including exceptions and footnotes.

United Kingdom

• Codes: the Companies House condensed SIC 2007 list, which is the list you choose from when filing.
• Headings and activities: the ONS UK SIC 2007 structure and alphabetical index, about 16,000 entries.
• SIC 2026: the ONS correspondence table from SIC 2007 to SIC 2026.

How US and UK codes are linked

There's no official table linking NAICS to UK SIC. We follow two official Census concordances (2022 NAICS to 2017 NAICS, then 2017 NAICS to ISIC Rev. 4, the UN classification) and match on the ISIC class, which UK SIC 2007 follows through the EU's NACE. That's why those links are labelled as the closest match, not an exact one.

Business-type guides

Each guide is written from the official index entries for that kind of business, checked against the definitions, and reviewed by a person before publishing. Every code in a guide is automatically checked against the current official data on every build.

Freshness

Last checked: November 14, 2026. NAICS data last changed November 14, 2026; UK SIC data last changed November 14, 2026.

See every file and link on the sources page.