A Federal Tax ID Number (FEIN) is a nine-digit number used by businesses for tax purposes. FEIN information isn't as closely guarded as Social Security numbers and in fact, the number is often freely available on the Internet. If the EIN belongs to a large, public company, you should be able to find the number's owner with little difficulty. However, if the number belongs to a small company (for example, a sole proprietorship), you may need to do a little more digging.
Look up the number on a reverse EIN website. Visit SECInfo.com and type the EIN into the "Search" box. Click on "Search." SEC Info searches the Securities and Exchange EDGAR database for the EIN and will return the name of the company at no charge if it is in the database (the EIN owner is a public company, this search will likely be a success). Best People Search offers a fee-based reverse search EIN number by state; you must know the state in which the business is located for the search to work. You can also try FEIN Search, which will perform a reverse EIN search for a fee.
Visit your local library and ask the reference librarian for assistance. Public libraries often have access to fee-based databases like ReferenceUSA and Lexis Nexis. If your library has access, you may be able to locate the EIN's owner for free.
Contact the Internal Revenue Service and ask for the name of the company that owns the EIN. The IRS agent will want to know the reason for your request. You may also be asked to divulge your identity (so the agent can ascertain whether you have a legitimate reason for the request).
Try entering the number into a search engine. Companies often list their EIN on websites, and the information is also listed on a variety of other websites reporting on company dealings. For example, a search of the EIN 31-0411980 reveals it's the EIN for Procter and Gamble.