Individuals filing tax paperwork identify themselves with their Social Security number. Many businesses use an EIN or employer identification number to do the same. Not every company has an EIN: a sole proprietor with no employees can often get by with the owner's Social Security number. There are several ways to conduct an EIN lookup for free, depending on the circumstances.
If you do business with the company, the tax ID lookup may be a slam dunk. For example, if they've opened an account at your bank, it'll have their EIN in the paperwork. If you've worked for them, the W2 or 1099 tax form they sent you will have their EIN on it.
If you have a legitimate reason to know the company's EIN, you can simply contact the business and ask for it. That's the quickest approach, but the company doesn't have to give out its EIN if you don't have a valid request.
The Securities and Exchange Commission stores business filings online in its Electronic Data Gathering, Analysis and Retrieval database. EDGAR is a free search tool available to the public. Enter a company name and you will see their filings. Many of the filings include the company's EIN. The SEC, however, only deals with publicly traded companies selling stock on an exchange. If the business is privately held, EDGAR can't help you.
If the company is a corporation, it will have to register with its state's division of corporations. The exact name of the division varies from state-to-state, but it's usually found online at the secretary of state's website. The website will have a place for you to research companies– plug in the business name and you may get an EIN back. Florida's Division of Corporations provides EINs for businesses registered in the state, for instance. Other states do not.
You can also look up limited partnerships and limited liability companies at the same state website. Other types of businesses, such as sole proprietorships, don't have to register.
Organizations that accept tax-deductible donations are a special case. They include churches, foundations, charitable organizations, fraternal organizations and many others organized under the IRS 501(c)3 rules.
The IRS has an online tool for looking up any tax-exempt organization. You can search by name or by the city or state, though using geography will generate a lot of results. The IRS information includes each organization's EIN among a host of other data.