>This might be of some assistance in weeding out fakes: https://www.irs.gov/businesses/small-businesses-self-employed/how-eins-are-assigned-and-valid-ein-prefixes
>
>And if it's really important (as in: you customer is willing to pay for a service): https://www.tincheck.com/ There are probably others who do this, also for a fee.
>
>The IRS has a manual process that is real-time, but seems to be web only.

Why did I expect that IRS would have a (free) web service for this? If USPS can have one that checks addresses (and returns them in normalized form)...