Whether a company's employer identification number can be found depends almost entirely on what kind of company it is. Three categories disclose it as a matter of course. Everything else does not, and for those the answer is to ask. Working out which category you are dealing with takes a minute and saves the rest of the search.
The three categories that disclose
Companies with registered securities print the number on the cover of every periodic filing. Tax-exempt organisations have it published alongside their annual information return, because exempt status is public. Recipients of federal contracts and grants carry an identifier in the award record. If the company you are checking falls into one of these, the number is a short search away and is reliable because the company itself put it there.
Everything else, and why
A privately held corporation or limited liability company with no securities registration, no exempt status and no federal awards has never been required to publish its number, and the IRS does not publish it either. That covers the large majority of US companies. No lookup service has privileged access to this: a service selling a search against private companies is selling the same public sources, or worse, a guess.
What to do instead, and what it proves
Request the number from the company using the standard taxpayer identification certification, which is the instrument designed for a payer to collect it from a payee. Alongside it, pull the state register record to confirm the legal name, entity type, status and registered agent. The two together are what a bank, a landlord or a procurement team is actually trying to establish, and only one of them was ever going to come from a search engine.
Questions people ask about how to find a company's ein
Why can I find some companies' EINs and not others?
Because only companies with securities filings, exempt status or federal awards have been required to publish the number. Private companies have not.
Do paid company EIN lookup services have more data?
No. They resell the same public sources. Where the number was never published, they do not have it either.
What is the correct way to obtain it?
Request it from the company with the standard taxpayer identification certification, and confirm the entity separately on its state register record.