SEC Filing Types Explained for Traders

Every SEC filing type tells a different story. This guide explains what each filing means, why it matters for stock prices, and how to trade the catalyst. All filings are tracked live in our scanner.

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8-K — Current Report (Material Event)

HIGH IMPACT

An 8-K is filed when a material event happens — earnings surprises, CEO changes, mergers, acquisitions, bankruptcies, or significant contracts. This is the most catalyst-rich filing type.

Why traders watch it

8-Ks often contain the first public disclosure of market-moving news. They can trigger same-day gaps of 5-50%+ depending on the event. The filing appears on EDGAR before most news outlets cover it.

Example: Company files 8-K disclosing acquisition offer at $45/share. Stock was trading at $32. Gap: +40% at open.
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10-K — Annual Report

MEDIUM IMPACT

The 10-K is the comprehensive annual financial report. Contains audited financials, management discussion, risk factors, and business overview. Most information is already known from quarterly reports and earnings calls.

Why traders watch it

Sometimes reveals hidden risks, restated financials, or going concern warnings not disclosed in 10-Qs. Compare year-over-year trends in revenue, margins, and debt levels. Late 10-K filings (see NT 10-K below) are a red flag.

10-Q — Quarterly Report

MEDIUM IMPACT

Unaudited quarterly financials filed 3 times per year (Q1, Q2, Q3 — the Q4 is covered by the 10-K). Contains income statement, balance sheet, and cash flow.

Why traders watch it

Revenue trajectory, cash burn rate, and margin expansion/compression. Often released same day as earnings, but may contain footnotes with material disclosures the earnings call skipped.

Form 4 — Insider Transactions

HIGH IMPACT

Filed within 2 business days when company insiders (officers, directors, 10%+ shareholders) buy or sell shares. Must disclose exact shares, price, and whether it was a purchase or sale.

Why traders watch it

Cluster buys — when multiple insiders buy within a short window — are one of the strongest bullish signals in finance. Insiders have the best information about their company's future. Academic research shows insider buying predicts outperformance.

Example: CEO buys $2M in shares, CFO buys $500K, and a director buys $200K — all within 5 days. Cluster buy signal.
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SC 13D — Activist Ownership Stake

HIGH IMPACT

Filed when someone acquires 5%+ of a company with intent to influence management. This is the activist investor filing — they want changes (board seats, strategy shift, spinoff, or sale).

Why traders watch it

SC 13D filings regularly trigger 10-30% moves. The activist premium comes from expected corporate changes: cost-cutting, asset sales, or outright acquisition. The filing includes the investor's stated intentions.

SC 13G — Passive Ownership Stake

LOW-MEDIUM IMPACT

Filed when someone acquires 5%+ of a company as a passive investment (no intent to influence management). Index funds and institutions file 13G, not 13D.

Why traders watch it

Watch for 13G → 13D amendments — when a passive holder converts to activist status. That transition is a major catalyst. Also watch for institutional accumulation patterns.

Track institutional signals →

SC TO-T — Tender Offer

HIGH IMPACT

Filed when a company makes a formal offer to buy shares of another company directly from shareholders. This is a public acquisition bid with a stated price and timeline.

Why traders watch it

Tender offers typically come at a 20-50% premium to current price. The spread between current price and tender price represents the merger arbitrage opportunity. Watch for competing bids that raise the price further.

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S-3 — Shelf Registration

BEARISH SIGNAL

Allows a company to sell new shares to the public at any time over the next 3 years. The filing itself doesn't mean shares will be sold immediately, but it signals the company is preparing to raise capital by diluting existing shareholders.

Why traders watch it

S-3 filings often cause 5-15% drops on the fear of dilution. Small-cap and biotech companies use these frequently. If followed by an actual offering, expect further downside.

NT 10-K / NT 10-Q — Late Filing Notification

RED FLAG

Filed when a company cannot meet its SEC reporting deadline. "NT" stands for "Notification of Late Filing." The company must explain why and provide an expected filing date.

Why traders watch it

Common reasons: accounting problems, auditor changes, internal control weaknesses, or pending restatements. Historically, NT filers underperform the market over the next 90 days. But if insiders are simultaneously buying, the delay may be procedural.

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DEFA14A — Proxy Solicitation Materials

MEDIUM-HIGH IMPACT

Additional proxy materials sent to shareholders before a vote. Often related to mergers, board elections, or activist campaigns. Multiple DEFA14A filings in succession signal an active proxy fight.

Why traders watch it

Proxy fights create volatility. Watch for competing DEFA14A filings from management and activist investors — each side trying to sway shareholders. The outcome can trigger significant repricing.

13F — Institutional Holdings Report

MEDIUM IMPACT

Quarterly report filed by institutional investment managers with $100M+ in assets. Discloses all equity holdings as of quarter end. Filed 45 days after quarter end.

Why traders watch it

Reveals where hedge funds and large institutions are positioning. When multiple independent funds increase positions in the same stock, it signals institutional consensus. The data is delayed (45 days) but still valuable for identifying trends.

Track 13F signals →

8-A — Securities Registration

LOW IMPACT

Filed to register a class of securities under Section 12 of the Securities Exchange Act. Usually filed by companies going public or listing on a new exchange.

Why traders watch it

Can signal upcoming IPO or exchange listing. Watch for 8-A filings combined with S-1 (IPO registration) for new listing opportunities.

Track all SEC filings in real time

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