A federal tax ID number for a business, also called a Taxpayer Identification Number (TIN), an Employer Identification Number (EIN), or a Federal Employer Identification Number (FEIN), is a nine-digit number that businesses required to file tax returns must obtain from the Internal Revenue Service. You can verify an EIN for a nonprofit organization or a public company for free.
Navigate to the Guidestar website listed in References.
Enter the employer's name in the search box, above "Start Your Search," then click the "Start Your Search" box.
Click on the charity name, then click on "Form 990 and Docs." The EIN should be listed on the first page of the 990.
Navigate to the Securities and Exchange Commission's Electronic Data Gathering Analysis & Retrieval (EDGAR) website listed in the References.
Click on "Search for Company Filings."
Click on a search parameter. You can search by name, ticker number, and a variety of other ways. How you search will depend on the information you have.
Click on "Find Companies" after you have entered your search parameters, then click on "CIK" in the left hand column. To view documents, click on the "documents" button, then click on the document ID number. The EIN will be on the front page of many filings, including (but not limited to) 10-Ks and 20-Fs.
To verify a private company's TIN, there are many for-fee services, including Knowx.com, FEINSearch.com, and LexisNexis.com.