There is no published information about Walmart employer's identification number. The best way to verify employer identification numbers (EIN) is to contact the business.
EINs are 9-digit long, if you're a Walmart employee, you can find this information on your W2 form. If you don't have your W-2 in hand, you can contact Walmart's payroll department at (479) 273-4323 or visit the associate website, WalmartOne.com to find information on how to download your W2.
As the tax season date approaches, most taxpayers will begin to receive needed documents. Find out when to expect tax documents from employers, including some deadlines for each form here.