# CIK

> The Central Index Key: the permanent number the SEC assigns to every filer.

Updated Oct 17, 2026.

The Central Index Key (CIK) is the number the SEC assigns to every person and entity that files on EDGAR: companies, funds, insiders and filing agents. It is permanent. A company keeps its CIK when it changes its name or its ticker, and a CIK is never reused.

## Format

Up to ten digits. SEC data files pad it to ten digits with leading zeros (`CIK##########.json`). Both forms identify the same filer.

## Why use it instead of a ticker

Tickers change, are reused by other companies, and differ between share classes of the same company. The CIK does not. Listed identifies companies by CIK behind the scenes and shows the ticker for convenience. `/companies/cik/<cik>` redirects to the company's page.

## Insiders have CIKs too

Every person who files a Form 3, 4 or 5 has a CIK of their own. Listed's insider pages are keyed by it, so one person's filings across several companies appear together.

## Related terms

- [EDGAR](/glossary/edgar.md)
- [Accession number](/glossary/accession-number.md)
- [SIC code](/glossary/sic-code.md)

## Guides that use it

- [Insider trades: what Form 4 tells you](/guides/insider-trades-what-form-4-tells-you.md)

All terms: [/glossary.md](/glossary.md)