What is an 8-K filing?

A Form 8-K ("current report") is how a U.S. public company tells the market that something material has happened, generally within four business days of the event. The 10-K and 10-Q arrive on a schedule. An 8-K arrives whenever an event triggers one.

Common 8-K items and what they mean

• Item 1.01 - Entry into a material agreement (contracts, partnerships, licensing deals).
• Item 1.03 - Bankruptcy or receivership.
• Item 2.01 - Completion of an acquisition or disposition.
• Item 2.02 - Earnings (results of operations). Most earnings press releases arrive as an 8-K first.
• Item 3.01 - Delisting notice from the exchange.
• Item 5.02 - Executive changes: CEO and CFO departures, appointments, and board changes.
• Item 7.01 / 8.01 - Regulation FD and "other events", the catch-alls for anything from clinical-trial results to contract wins.
• Item 1.05 - Material cybersecurity incidents (required since December 2023).

That is the short list. For every item number, including rare ones like restatements (4.02) and changes in control (5.01), and counts of how often each appears, see the full 8-K item reference.