All businesses in the United States must apply for a Federal Identification Number, also called an Employer Identification Number (EIN). This number allows the Internal Revenue Service (IRS) to identify and track all employers for tax purposes. Because the EIN is specific to a single business, business owners who receive an EIN must protect it much like an individual protects their Social Security number.
Look for the notice you were issued by the IRS when you were assigned your EIN. The number should be on the confirmation page.
Contact any bank you have an account with under the business name. They will have your EIN, as will any county or state office you used to apply for any licenses.
Call the IRS Business & Specialty Tax Line at (800) 829-4933 to ask for your EIN. You will be asked a series of questions to establish your identity. The Tax Line is available Monday through Friday from 7 a.m. to 10 p.m. local time.
Use a company like FEIN Search to look up an employer's EIN if you are not the owner of the business. FEIN Search offers paid subscription access to its database.