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SEC Filings for Insider Trading, Explained
Updated 2026-06-16. A developer-focused map of the SEC filings that reveal what insiders and institutions are doing — what each form reports, how they connect, how to read the signal, and how to pull them programmatically.
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Insider activity is disclosed on SEC Form 4 (transactions, within 2 business days), Form 3 (initial holdings), and Form 5 (annual catch-up); Form 144 signals an insider's intent to sell ahead of time; and 13F-HR reports the quarterly holdings of large institutions. Form 4 carries the most signal because it is fast, transaction-level, and flags whether a trade was a discretionary open-market purchase.
The filings that move markets
Five SEC forms carry almost all of the signal for insider and institutional analysis. Three of them (Forms 3, 4, and 5) come from Section 16 of the Securities Exchange Act and cover company insiders; Form 144 covers proposed sales of restricted stock; and 13F-HR covers large institutional managers. Each links to its deep-dive guide where one exists.
| Form | What it reports | Timing | Signal |
|---|---|---|---|
| Form 3 | Initial statement of beneficial ownership — everything an insider already holds. | Within 10 days of becoming a director, officer, or 10%+ owner. | Baseline, not a signal |
| Form 4 | A change in an insider’s holdings — open-market buys and sells, grants, option exercises. | Within 2 business days of the transaction. | High — open-market buys especially |
| Form 5 | Annual catch-up for transactions exempt from, or missed on, Form 4. | Within 45 days of the issuer’s fiscal year end. | Low — mostly compensatory |
| Form 144 | Notice that an insider intends to sell restricted or control shares. | Filed before the sale; sale must occur within 90 days. | Forward-looking sell intent |
| 13F-HR | Quarterly holdings of institutional managers with $100M+ in 13(f) securities. | 45 days after quarter end. | Context — slow, but shows the big holders |
All of these are filed electronically through the SEC's EDGAR system and are public the moment they are submitted.
How the filings connect
The forms are most useful read together rather than in isolation. A new officer or director files a Form 3 to establish their starting position, then a Form 4 for every subsequent trade. When that insider plans to sell restricted or control shares, a Form 144 is filed before the sale — so Form 144 is the forward-looking intent and the later Form 4 is the backward-looking confirmation. Joining the two gives a complete intent-to-action picture for insider sales.
13F-HR sits in a different layer entirely: it shows the institutional ownership backdrop a company trades against, but with a 45-day lag it is context, not a trigger. The timely, actionable layer is Form 4 — and the strongest reads within it are cluster buys, where several insiders buy in the same window.
Reading the signal
Not every filing is meaningful. The single most important field on a Form 4 is the transaction code: an open-market purchase (code P) is high-signal because an insider generally buys for only one reason, whereas grants, tax-withholding, and option exercises are mechanical. A practical filter for signal work is:
- Open-market transactions only — exclude grants (A), tax withholding (F), and option exercises (M).
- Exclude Rule 10b5-1 plan trades, which are pre-scheduled and carry no information advantage.
- Weight officers and directors over passive 10%+ holders.
- Prioritise clusters over single trades.
The Form 4 guide covers every transaction code in detail, and the screener and signals tools apply these filters over live data.
Accessing the filings programmatically
Every filing above is free on EDGAR, but EDGAR ships verbose XML with company and insider metadata split across separate documents, and ticker / CIK / CUSIP joins need additional reference data. The insider trading API skips that work: it returns parsed Form 4, Form 144, and 13F-HR records as JSON, already joined and amendment-aware, with real-time webhooks on every new transaction and a genuine free tier.
See the API docs for the full endpoint reference, how Form4API compares to other insider-trading and SEC filing data providers, or read the deep-dive guides below.
All guides
SEC Form 4 explained
Who files, transaction codes, the 2-day rule, and how to read insider filings.
Read guideForm 4 transaction codes
The complete list of Form 4 transaction codes — P, S, A, F, M and the rest — with meaning and signal weight.
Read guideForm 3 and Form 5 explained
The initial-ownership filing and the annual catch-up — what each reports and why they matter less than Form 4.
Read guideHow far back does insider data go?
EDGAR has electronic Form 4 filings back to 2003; Form4API serves complete history from April 2023.
Read guideSEC Form 144 explained
Notice of proposed sale — thresholds, the 90-day window, and how it leads Form 4.
Read guide13F-HR filings explained
Institutional holdings — the $100M threshold, the 45-day lag, and CUSIP mapping.
Read guideInsider vs congressional trading
How SEC Form 4 insider data differs from STOCK Act congressional trades — law, deadlines, and precision.
Read guideCluster buy signals
Why multiple insiders buying together is the strongest insider signal.
Read guide10b5-1 trading plans
Why pre-scheduled insider trades carry less signal, and how to filter them out.
Read guideBacktesting insider trades on QuantConnect
Export Form 4 trades as CSV and backtest them in a LEAN algorithm, keyed on the filing date.
Read guideGet insider data in Python
Pull parsed Form 4 data with requests, filter for open-market buys, and subscribe to webhooks.
Read guideConnect AI agents via MCP
Give Claude, Cursor, or any MCP client live SEC insider data with one npx command and a free key.
Read guideInsider data in Google Sheets
Pull live Form 4 transactions into a spreadsheet with a copy-paste custom function — no server.
Read guideBest insider trading API
How to choose an insider trading API, the main provider categories, and where Form4API fits.
Read guideOpenInsider vs ShareSeer vs Form4API
Free screener websites vs a developer API with webhooks and MCP — an honest look at when each fits.
Read guideInsider trading webhooks
Real-time Form 4 alerts: register an endpoint, verify the HMAC signature, and handle retries.
Read guideInsider trading screener
Filter SEC Form 4 by code, the significant preset, trade size, post-trade returns, and more.
Read guideTop insiders by track record
Rank insiders by the hit rate and average return of their open-market buys — and read it honestly.
Read guideDo insider buys outperform? (study)
A data study of 45,000 open-market buys vs sells: returns at 1, 3, and 6 months, with an honest method.
Read guideWhy insiders sell — signal vs noise
Diversification, tax events, and 10b5-1 plans explain most sells. Here is how to spot the minority that signals real bearish intent.
Read guideInsider buys after selloffs (study)
A data study: insider buys during deep selloffs averaged +10.9% at 3 months vs +6.3% near highs — with an honest look at the median.
Read guideDoes insider selling predict drawdowns? (study)
A data study of 194,000 sells: discretionary sells underperform planned ones, and the bearish signal concentrates in selling into weakness.
Read guideFrequently asked questions
Which SEC filings show insider trading?
Insider trading is disclosed primarily on SEC Form 4, which every director, officer, and 10%+ shareholder must file within 2 business days of buying or selling their company’s stock. Form 3 reports an insider’s initial holdings, and Form 5 is an annual catch-up for exempt or missed transactions. Form 144 is filed before an insider sells restricted or control shares, so it signals intent ahead of the Form 4 that later confirms the sale. For institutional (not insider) positions, 13F-HR reports the quarterly holdings of large money managers. Form 4 is the filing most analytical workflows rely on because it is fast, transaction-level, and includes a code that distinguishes a discretionary purchase from a compensatory grant.
What is the difference between Form 4 and 13F?
Form 4 and 13F-HR describe two different kinds of owner. Form 4 covers company insiders — directors, officers, and 10%+ holders — and is filed within 2 business days of each individual transaction, so it is timely and granular. 13F-HR covers institutional investment managers with at least $100 million in qualifying U.S. equities, and is filed only once a quarter with a 45-day lag, so by the time it is public the positions can be three to four months old. Use Form 4 to see what insiders are doing right now; use 13F-HR for slower-moving context on which institutions hold a name.
How quickly are SEC insider filings public?
A Form 4 must be filed within 2 business days of the transaction, and it appears on the SEC’s EDGAR system the moment it is submitted — there is no review delay on the raw filing. Form 144 is filed before the sale happens. 13F-HR is the slow one: it is due 45 days after the quarter closes. Commercial APIs add parsing and ticker/CIK/CUSIP joins on top of EDGAR; Form4API ingests new Form 4 filings in real time from EDGAR's getcurrent feed, typically surfacing them in its REST endpoints and webhooks within about a minute of SEC acceptance.
Can I get SEC filing data through an API?
Yes. The raw filings are free on EDGAR, but parsing the XML and joining it to ticker, CIK, and CUSIP metadata is non-trivial, which is why commercial APIs exist. Form4API exposes parsed Form 4, Form 144, and 13F-HR data as a REST API with real-time webhooks, amendment-aware parsing, and a genuine free tier — so you can query insider transactions by ticker or subscribe to new filings instead of scraping EDGAR yourself. See the insider trading API and the docs to get started.
Which SEC filings are most useful for trading signals?
Open-market purchases on Form 4 (transaction code P) carry the most signal, because an insider generally buys for only one reason — they expect the stock to rise — while sales have many innocent explanations. The signal strengthens when several insiders at the same company buy together (a cluster buy) and weakens when a trade was pre-scheduled under a Rule 10b5-1 plan, which carries no information advantage. A practical filter is: open-market only, exclude 10b5-1 plan trades, focus on officers and directors, and look for clusters rather than single trades.