An Employer Tax ID, also called an Employer Identification Number (EIN) or a Tax Identification Number (TIN), is a nine digit number used by the IRS to identify a business entity. This number is often required when completing your taxes. This makes locating your employer's tax ID a critical matter. Methods for looking up an employer's tax ID can range from the very simple to the complex and costly. It is best, of course, to start with the simplest approach and move on from there.
Check the IRS Form W2 that you receive at the beginning of the year from your employer. According to the Instruction for Form W2 the Employer Identification Number is located in box b in the top right corner.
Check other documents you have received from the employer. The tax ID number could be located on an invoice or a pay stub.
Contact the employer. Call the employer's human resources department. Explain why you need the information and there shouldn't be any reason the company won't provide the EIN.
Locate other documents the employer has filed with the government. According to the U.S. Department of Labor an employer's tax ID number can be found on Security and Exchange Commission Form 10-K and Form 20-F as well as IRS Form 990.
Pay an online company to use their employer tax ID database. There are dozens of companies that specialize in tracking down EINs to create a vast database that can be searched online. This will often require that you establish an account or subscription with the service provider and pay a fee.