Forensic · 13D/13G

Schedule 13D filings: How activist disclosures move stock prices

When an investor crosses the 5% ownership threshold of a public company with intent to influence control, they must file Schedule 13D within 10 days. The filing discloses their identity, ownership stake, and — critically — their plans.

Schedule 13D vs. 13G

Schedule 13D is for activist investors. Schedule 13G is for passive investors (index funds, asset managers) crossing the 5% line without intent to influence. The same investor can convert from 13G to 13D when their intent changes.

What's in a 13D

The filing has 7 standardized items. The interesting ones:

• Item 4 (Purpose of Transaction) — what the activist intends. Sometimes specific ("seek board representation"), sometimes vague ("evaluate strategic alternatives")
• Item 5 (Interest in Securities) — exact ownership percentage and recent purchases
• Item 6 (Contracts, Arrangements, Understandings) — any partnerships with other investors

Why activist identity matters

A 13D from Carl Icahn or Elliott Management has different market reaction than one from a less-known fund. Known activists with track records:

• Icahn Enterprises — usually pushes for board seats or strategic changes
• Elliott Management — aggressive in pushing for sales or breakups
• Engine No. 1 — climate-focused activism (famous for Exxon)
• Starboard Value — operational improvements
• Bulldog Investors — closed-end fund discount activism
• Saba Capital — also closed-end fund activism

Market reaction patterns

Common reactions on 13D filing:

• Immediate 5-15% stock pop on activist announcement
• Larger pops if the activist is well-known
• Sustained move if the campaign produces actual changes (board seats, breakup, sale)
• Reversal if the activist exits without changes

FilingFirehose and 13D tracking

FilingFirehose's daily SEC newsletter (separate product from Forensic) flags 13D filings with known activist filers in real time. Forensic's risk algorithm currently does not weight 13D filings — they're more "opportunity" than "red flag" — but they're tracked in the broader FF API.

Free risk score: filingfirehose.com/forensic