SEC Filings and their meanings

SEC filings are very critical documents that every trader and investor need to access and read. So here are the common SEC filings and their intended purposes. For more information please visit https://en.wikipedia.org/wiki/Category:SEC_filings

1. 10K - represents the annual report that every company listed in NASDAQ, NYSE or AMEX should post in sec.gov site. This document is an audited document. See "How to read a 10-K" from investor.gov website for more information.
2. 10Q - This is the quarterly report of a company which is unaudited.
3. 8K - If a company has news, events or press releases, they will go into the 8K report. For more information see "How to read an 8-K" from investors.gov website.
4. DEF 14A - Definitive Proxy Statement. When a company tells about executive compensations, election of its Board of Directors, Stock Offering or perhaps company mergers, the report will go into DEF 14A. If it is called PRE 14A, then it means it is a preliminary proxy statement.
5. Form 4 - This reports the purchase or sale of Stocks by Insiders. We refer these Insiders as Executive, CEO, President, VP or anyone who have a high position in a public company. We have heard about illegal insider trading. Yes, they happen from time to time, but if a company follows the rule then the process and actions are legal. Thus, public companies need to file a Form 4 if any of the insiders buy or sell stocks or when they get stock options or when they exercise stock options. There are cases when an executive cannot buy or sell stocks or exercise his options. When certain News of his company has not been made public yet, he/she should buy/sell or exercise his options. One example of this is with the pharmaceutical companies. When the result of a drug approval has been released but not made public yet, the executive cannot exercise his right to buy and sell shares. Of course in every rule, there is always an exception. 
6. SC13G - This report provides to the public visibility of a purchase or sale by large stock holders having more than 5% stake of the company. Mutual Funds and Hedge Funds who have more than 5% of the overall shares of the company should file this report.
7. SC13D - This report is used by Activist Investors. When a Hedge Fund or Investor seek to buy stock with more than 5% of the overall shares of a company with the purpose of influencing the Management to sell such company, then they should file this report called SC 13D. 
8. /A - If you happen to see reports appended with /A then it indicates that the filing has been amended. This is usually done when there are accounting anomalies from the previous report.
9. NT10Q or NT10K - If a company feels that they are going to be late in filing their quarterly or annual report, then they have to file NT10Q or NT10K.
10. 10QSB, 10KSB - When a company is too small like having a capitalization of 100M and they are listed as public companies, they are still required to file their Balance Sheets, Cash Flow Statements and Earnings Statements. All these Statements will go into the 10QSB for quarterly statements and 10KSB for annual statements.
11. S-3 - This report is called Registration of Securities. When a company needs to sell stocks an S-3 form should be reported. It is called Self-Registration if selling is done from time to time. It is termed as General Registration if the company sell stocks at one time to a big investor. 
12. S-8 -  A company need to register securities if it will give stock option plan to its employees or hand over stock shares. And the report is called S-8 when these securities are registered.
13. 20F - This is 10-K in reality. But it is named as 20F when the public company involve is based in another country, other than USA. 
14. 6F - This is also called 8K and 10Q but names as 6F only for companies that are based outside USA. USA based companies are asked to file every quarter for their statements. If a company is from overseas then they are required to file their statements every 6 months. Most of the time for foreign companies, the filings are done semi-annually or annually. 
15. CT ORDER - Confidential Treatment Order. A company can request for Confidential Treatment on some information they deemed confidential and should not be released to the public in their 10K or 10Q filings within specified time.  Example: TESLA asked for extension of Confidential Treatment Order "ORDER GRANTING CONFIDENTIAL TREATMENT UNDER THE SECURITIES EXCHANGE ACT OF 1934" last Sep. 21, 2020 for information not to be included in their 10K and 10Q filings of 2017-2018 to be extended to Sep. 20, 2023. 
16. SD - Specialized Disclosure Form. This is to inform the public of special disclosures concerning a company's manufacturing processes involving the use of materials that maybe considered Conflict Minerals. eg. Conflict Minerals Report of LPTH