An Employer Identification Number (EIN) is granted to a business by the IRS for tax-filing purposes. If you need to find an EIN for a business, many search engines online can help you do so. However, searching for a business and its address based on an EIN is a bit more tricky--but it can be done.
Use the IRS website if the business you're trying to find is a non-profit organization. You can enter the EIN into the e-Postcard Search Page (see Resources) to return information about that organization, including its address.
Call the IRS Business line at 800-829-4933 and wait for your call to be taken.
Ask the representative who answers your call if you can search for a business's address based on the Employer Identification Number. Just a warning: you might have to explain to the representative how you obtained the EIN in the first place.