SEC Filings Cheat Sheet: Every Filing Type Explained

Every publicly traded company in the U.S. is required to file documents with the Securities and Exchange Commission. These filings contain critical information about offerings, financials, insider transactions, and corporate events — often before the market fully prices them in.

This guide breaks down every major SEC filing type into plain English, organized by category. Bookmark it. Come back to it every time you see an unfamiliar filing hit EDGAR.

How SEC Filings Work

All SEC filings are submitted through EDGAR (Electronic Data Gathering, Analysis, and Retrieval), the SEC’s public database. Filings become publicly available shortly after submission, with one important exception: EFFECT notices are batch-released daily at 6:00 AM ET.

Understanding the difference between filing and effectiveness is critical. A registration statement (like an S-1 or S-3) is just a request. The SEC reviews it, may require amendments, and eventually declares it “effective” — only then can the company actually sell securities.

Dilution & Offering Filings

These are the filings that directly impact share count and are most relevant to traders watching for dilution events.

Registration Statements

S-1 / F-1 — The initial registration statement. Used for IPOs, follow-on offerings, and resale registrations. The first page will tell you which type it is — look for “initial public offering” or “resale” language. F-1 is the foreign private issuer equivalent. Price impact varies: IPOs are typically priced in advance, but surprise follow-on registrations for small caps can move the stock significantly.

S-1/A, F-1/A — Amendments to the original registration statement. The SEC almost always requires at least one round of amendments before granting effectiveness. Each amendment can contain updated financial data, revised share counts, or new risk factors. Watch for changes in the offering size between amendments.

EFFECT — This is the SEC’s stamp of approval on a registration statement. Not a filing by the company itself — it’s issued by the SEC. All EFFECT notices are released in a daily batch at 6:00 AM ET. For large-cap IPOs, effectiveness is expected and priced in. For small-cap offerings, an EFFECT notice often signals that pricing and dilution are imminent — sometimes within hours.

S-1MEF / F-1MEF — A “manual of effectiveness” filing that allows a company to upsize an offering by up to 20% after the original registration is already effective. This catches many traders off guard because it increases the deal size without a new registration process.

Shelf Registrations

S-3 / F-3 / F-10 — Shelf registration statements. These allow a company to register securities and sell them at any point over the next three years. Think of it as pre-authorization to raise capital. An S-3 filing alone doesn’t mean dilution is happening — it means the company can dilute when it chooses to. The actual sale is disclosed later via a 424B5. Also used for resale registrations (existing shareholders registering shares for public sale). F-10 is the Canadian issuer equivalent.

S-3ASR / F-3ASR — Automatic shelf registration, available only to “Well-Known Seasoned Issuers” (WKSIs) — companies with a public float exceeding $700 million. These become effective immediately upon filing, with no SEC review period. Large caps can go from filing to selling securities in a single day.

S-3MEF / F-3MEF — Shelf upsizing, similar to S-1MEF. Signals that the company is about to use its shelf and may need more capacity. Often filed alongside or just before a 424B5.

Prospectus Supplements (The 424B Family)

These are the filings that disclose the actual terms of a securities sale. When a company goes from “we registered shares” to “we’re selling shares,” it shows up here.

424B5 — The most important prospectus supplement for tracking dilution. It has three distinct use cases:

At-the-market (ATM) offerings: The company sells shares gradually into the open market at prevailing prices. Look for language like “at-the-market offering program” or “sales agreement.”
Overnight/underwritten offerings: A one-time block sale, usually at a discount to market price. These are typically priced after hours and filed the next morning.
Warrant/convertible note exercise registrations: Discloses terms when warrants are being exercised or convertible notes are being converted into common stock.

424B4 — The final prospectus filed after an IPO or offering is completed. Contains the definitive pricing, share count, and use of proceeds. By the time this is filed, the deal is done.

424B3 — Filed after a resale registration receives its EFFECT, or to update a prior prospectus with material changes. Common for PIPE (private investment in public equity) deals where investors need their shares registered for resale.

424B2 — Typically used for structured note or debt offerings. Less relevant for equity dilution tracking but important for understanding a company’s debt issuance activity.

Other Offering-Related Filings

RW — Registration withdrawal. The company is pulling a previously filed registration statement. This can be bullish (the company no longer needs to raise capital) or meaningless (they’re refiling with different terms). Context matters.

S-4 / F-4 — Registration of shares to be issued in a merger or acquisition. If Company A is acquiring Company B in a stock deal, Company A files an S-4 to register the new shares it will issue to Company B’s shareholders.

S-8 — Registration of shares under employee benefit plans (stock options, RSUs, ESPP). These are usually routine and rarely move the stock, but they do increase the total share count over time.

Regulation A+ Filings

Regulation A+ is a “mini-IPO” framework that allows smaller companies to raise up to $75 million from the public with lighter disclosure requirements than a traditional S-1.

1-A: The offering circular (equivalent of an S-1)
1-K: Annual report (equivalent of a 10-K)
1-SA: Semi-annual report (equivalent of a 10-Q)
1-U: Current event report (equivalent of an 8-K)

Financial Filings

These are the core periodic reports that disclose a company’s financial health.

Quarterly & Annual Reports

10-Q — Quarterly financial report, filed three times per year (Q1, Q2, Q3 — the Q4 data is included in the 10-K). Filing deadlines depend on filer category:

Large accelerated filers (float > $700M): 40 days after quarter-end
Accelerated filers (float $75M–$700M): 40 days
Non-accelerated filers (float < $75M): 45 days

Key sections to review: revenue trends, cash burn rate, debt covenants, and the “going concern” language in the auditor’s notes.

10-K — Annual financial report, the most comprehensive disclosure a company makes each year. Filing deadlines:

Large accelerated filers: 60 days after fiscal year-end
Accelerated filers: 75 days
Non-accelerated filers: 90 days

The most valuable sections are Management’s Discussion & Analysis (MD&A), risk factors, and subsequent events (things that happened after the reporting period but before filing).

20-F — Annual report for foreign private issuers. Due within six months of fiscal year-end. Same depth as a 10-K but follows international reporting conventions.

40-F — Annual report for Canadian companies cross-listed in the U.S. Filing deadline matches Canadian regulatory requirements.

Red Flag Filings

NT 10-Q / NT 10-K — “Non-timely” notification. The company is telling the SEC it cannot file its quarterly or annual report on time — a red flag. Common reasons include accounting irregularities, auditor disagreements, or internal control weaknesses. Companies get a 5-day extension (10-Q) or 15-day extension (10-K), but the filing itself signals trouble.

10-K/A / 10-Q/A — Amended financials. These restate or correct previously filed reports. Minor amendments (exhibit corrections, formatting fixes) are routine, but material restatements of financial results can trigger SEC investigations and shareholder lawsuits.

Material Event Disclosures

These filings cover everything that happens between periodic reports — the breaking news of SEC filings.

8-K — Current report disclosing material events. Must be filed within four business days of the triggering event. The 8-K is organized by item numbers, each covering a different category of event:

8-K Item Number Breakdown

Item 1.01 — Entry into a material agreement (partnerships, licensing deals, major contracts)
Item 1.02 — Termination of a material agreement
Item 1.03 — Bankruptcy or receivership
Item 2.01 — Completion of acquisition or disposition of assets
Item 2.02 — Results of operations (earnings releases are often filed here)
Item 2.03 — Creation of a direct financial obligation (new debt)
Item 2.04 — Triggering events that accelerate financial obligations
Item 2.05 — Costs associated with exit or disposal activities (restructuring, layoffs)
Item 2.06 — Material impairments (write-downs of asset values)
Item 3.01 — Notice of delisting or failure to meet listing standards
Item 3.02 — Unregistered sales of equity securities (private placements)
Item 3.03 — Material modification of shareholder rights
Item 4.01 — Changes in accountant (auditor changes — potential red flag)
Item 4.02 — Non-reliance on previously issued financials (restatement incoming)
Item 5.01 — Changes in control of the company
Item 5.02 — Departure/appointment of directors or officers (C-suite changes)
Item 5.03 — Amendments to articles of incorporation or bylaws
Item 5.07 — Submission of matters to a vote of shareholders
Item 7.01 — Regulation FD disclosure (material info shared equally with all investors)
Item 8.01 — Other events the company considers important
Item 9.01 — Financial statements and exhibits

The highest-impact items are typically 1.01 (new deals), 2.01 (acquisitions), 2.02 (earnings), 3.01 (delisting risk), 4.02 (restatements), and 5.02 (leadership changes).

6-K — The foreign private issuer equivalent of an 8-K. Filed “promptly” after a material event (no specific day count). Covers the same categories of events but follows international disclosure conventions.

Ownership & Insider Filings

These filings track who owns what — from activist investors building positions to executives selling stock.

Institutional Ownership (Schedules 13D & 13G)

Schedule 13D — Filed when an investor acquires more than 5% of a company’s shares with the intent to influence or control the company. Must be filed within 10 business days. The filing includes the investor’s plans and intentions — whether they want board seats, a merger, a strategic change, or other activism. This is the filing that signals an activist campaign.

Schedule 13G — Filed when an investor acquires more than 5% passively, with no intent to influence. Filing deadlines are more relaxed: 45 days after calendar year-end for most filers, or within 10 business days if the stake exceeds 10%.

13D/A — Amendment filed when an activist’s position changes by more than 1% (up or down), or when their intentions change. Watch for stake increases (doubling down) and stake decreases (potentially exiting).

13G/A — Amendment to passive ownership filings. Deadlines vary by investor type but are generally annual updates unless there’s a material change.

The 13G-to-13D switch: When a previously passive investor converts their 13G filing to a 13D, it signals they’ve decided to take an active role. This is often one of the strongest bullish signals in ownership filings — a large, passive holder is now an activist.

Insider Ownership (Forms 3, 4, and 5)

Form 3 — Initial statement of beneficial ownership, filed within 10 days of becoming a company officer, director, or 10% beneficial owner. Establishes the baseline for all future insider transaction tracking.

Form 4 — The most-watched insider filing. Reports any change in an insider’s ownership and must be filed within two business days. Key transaction codes to understand:

P — Open-market purchase (generally bullish — the insider is buying with their own money at market price)
S — Open-market sale
A — Grant or award (stock compensation, not a market transaction)
M — Exercise of options or conversion of derivative security
G — Gift of securities
F — Payment of exercise price or tax liability through share surrender
C — Conversion of derivative security

The most meaningful signal is a P (purchase) transaction, especially cluster buying by multiple insiders. Routine S (sale) transactions under a pre-arranged 10b5-1 plan are typically less informative — the executive set up the sales in advance, often for tax planning purposes.

Form 5 — Annual catch-up filing for transactions that should have been reported on Form 4 but were not. Due within 45 days of the company’s fiscal year-end. A Form 5 filing often points to lax compliance practices.

Form 144 — Notice of proposed sale of restricted securities. Filed when an insider intends to sell restricted or control shares under Rule 144. This is a forward-looking signal — the insider is declaring they plan to sell, but haven’t yet.

Proxy & Governance Filings

Proxy filings relate to shareholder meetings, votes, and corporate governance decisions.

DEF 14A — Definitive proxy statement for annual shareholder meetings. Contains executive compensation details, board nominee biographies, shareholder proposals, and governance policies. The “Say on Pay” vote results are closely watched for controversial compensation packages.

PRE 14A — Preliminary proxy, filed at least 10 days before the definitive version. Gives the SEC time to review. For routine annual meetings this is standard procedure, but for special meetings it can signal upcoming corporate actions.

DEFM14A — Merger proxy. Filed when shareholders must vote on a proposed merger or acquisition. Contains the full transaction details: price, terms, fairness opinion, and the board’s recommendation. Required reading if you hold shares in a company that’s being acquired.

DEFA14A — Additional definitive proxy solicitation materials. Companies file these when they need to send supplemental information to shareholders after the main proxy has been distributed, often to respond to activist campaigns or clarify voting matters.

Activist Proxy Filings

PREC14A — Preliminary contested proxy. Filed by activists or dissidents proposing alternative board candidates.
PRRN14A — Preliminary proxy filed by a non-management party in a contested election.
DFAN14A — Definitive additional solicitation material from activists, often containing their case for why shareholders should vote for their slate of directors.

Proxy fights are most common at companies with underperforming stock prices, controversial management decisions, or governance concerns.

Other Important Filings

These filings do not fit neatly into the categories above but are still important for investors tracking corporate actions.

425 — Communications related to a pending merger or business combination. Companies file these to ensure all merger-related public statements are properly disclosed. Includes press releases, presentations, and employee communications about the deal.

SC TO-T / SC TO-I — Tender offer filings. SC TO-T is filed by a third party making a tender offer to acquire shares. SC TO-I is filed when a company makes a tender offer for its own shares (a buyback). These contain the offer price, conditions, and expiration date.

SC 14D-9 — The target company’s official response to a tender offer. This is where the board recommends shareholders accept, reject, or take no action on the offer. Often includes a fairness opinion from an investment bank.

15-12G / 15-15D — Deregistration filings. The company is “going dark” — suspending its SEC reporting obligations. This typically happens when a company goes private, falls below the shareholder threshold, or delists. Once effective, the company stops filing periodic reports.

25-NSE — Notification of delisting from a national securities exchange. Filed by the exchange itself (NYSE, Nasdaq) when a company is being removed from trading. Precedes the actual delisting.

How to Monitor SEC Filings

Knowing what each filing means is only half the equation. You also need a system for catching them in real time.

EDGAR Full-Text Search: The SEC’s own search tool at efts.sec.gov lets you search across all filings by keyword, company, or filing type.
EDGAR Company Filings: Search for any company on sec.gov and set up RSS feeds for specific companies or filing types.
Automated Alerts: Set up email or push notifications for specific filing types on the tickers you care about. The SEC offers RSS feeds, and many third-party services provide real-time EDGAR alerts.

The most effective approach combines automated alerts for your watchlist with a habit of checking EDGAR directly when you’re evaluating a new position.

Quick Reference Table

Filing	What It Means	Typical Impact
S-1 / F-1	IPO or offering registration	Low–Medium
EFFECT	SEC declares registration effective	Medium (small caps)
S-3 / F-3	Shelf registration (3-year authorization)	Low
424B5	ATM, offering pricing, or warrant exercise	Medium–High
424B4	Final IPO/offering prospectus	Low (deal is done)
10-Q	Quarterly financials	Varies
10-K	Annual financials	Varies
NT 10-Q/K	Late filing notification	Negative
8-K	Material event disclosure	Varies by item
SC 13D	Activist investor > 5% stake	Medium–High
SC 13G	Passive investor > 5% stake	Low
Form 4	Insider buy/sell within 2 days	Low–Medium
Form 144	Insider plans to sell restricted shares	Low
DEF 14A	Annual meeting proxy	Low
DEFM14A	Merger vote proxy	Medium
SC TO-T	Third-party tender offer	High
25-NSE	Exchange delisting notice	High (negative)
RW	Registration withdrawal	Low–Medium

Understanding SEC filings gives you an information edge that most retail investors overlook. The filings are public, free, and available in real time — the only barrier is knowing what to look for. Use this guide as your reference whenever an unfamiliar filing crosses your screen.