My friend and I are working on a website, with a feature being to allow company employees to create accounts and perform actions as official representatives of their company. For example, our website will allow a recruiter from Microsoft to create an account and recruit on there on behalf of Microsoft. In order to prevent random people from posing as official employees, we wanted to have some sort of official verification when an employee creates an account*. We've been toying around with the idea of using IRS information such as EIN and SSN as well as some sort of an API that can search an IRS database, but every API/web service we find isn't really helpful.
If anyone knows how to do this, advice would be greatly appreciated. Our website, for the record, uses JavaScript/HTML/CSS for front end and ExpressJS/PostgreSQL for back end.