There are many difficulties in researching private companies, defined here as companies that do not trade on stock exchanges. Consequently, researching private companies often requires considerable creativity and patience.
Unlike public companies, private companies are not required to file with the Securities and Exchange Commission (SEC), so the type of information and the depth of information that can be found in those documents is not necessarily going to be available for private companies. There are however, two exceptions that can be used in limited cases. First, if the company you are researching merged with or was acquired by, a public company it is possibly that the public company may provide investors information about the deal via SEC filings. Second, if the company was once public but goes private, previous SEC filings will still be available and may can be helpful for a limited time.
After exhausting some of the more basic directories that are found in the Basic Information section, the sources and strategies suggested below might reveal more information. Keep in mind that for many companies, it is likely going to be hard to find information beyond name and location.
Below are databases and openly accessible sources that are company information - location, contact information, officers. It may be that you will find important information on private companies and their executive in full-text articles. For more general full-text news sources available at the Library of Congress see the Searching for the News tab.
The subscription resources marked with a padlock are available to researchers on-site at the Library of Congress. If you are unable to visit the Library, you may be able to access these resources through your local public or academic library.
On July 18, 2023 the staff of Business Reference Services hosted a webinar going over how to do private company research. We went over some of the databases and websites as well as focusing on some strategies that may be particularly helpful.
If you are looking for the text transcript one is available.