Look for the employer tax identification number on any tax return filed by the company, if you work for the company or have access to the returns. Find a company's California employer account number on any California employment tax filing.
Contact the company directly to obtain its tax identification number if you do not work for the company but have a legitimate reason to obtain the number. Send a letter requesting completion of an IRS Form W-9, and enclose the form. The W-9 form provides the employer's name and tax identification number. You can obtain the form from the IRS or online legal services providers.
Locate a misplaced identification number by finding the official document on which the IRS issued the number. You can also contact any banks or agencies to whom the company provided the number as part of an account application. Alternatively, contact the Internal Revenue Service Business & Specialty Tax Line, (800) 829-4933, from 7:00 a.m. to 7:00 p.m. weekdays. Be sure you have information about the original filing in order to confirm your right to the number.