You only need to enter some basic information to obtain your free trial including name, email, postal address and company name. Once you have your free trial, you can search by company name, state, zip code or industry code. The database holds over seven million official ID numbers assigned by the IRS to U.S. Businesses including corporations, partnerships, LLCs, proprietorships, trusts and estates. All businesses operating in the US need an EIN, also known as a Federal Tax Identification Number, so these kind of databases are a great way to find official data on any business and can also help you to verify that companies are who they claim to be before you do business with them.
The only other way to find Employer Identification Numbers would be to spend time trawling through public records and filings, but this is an extremely time consuming process and you may not find what you want. This is why websites such as EINFinder exist and why you have the pay for the service, because it cuts out the time and effort you would have to spend finding the information you want otherwise.