I have a FEIN (Federal Employer Identification Number) and need to locate the business or non-profit that has been assigned that number, how can I look that up only given the FEIN number?
I think much of that info is hidden behind pay-walls. Here is one site I've found.
Another that is for non-profits only is guidestar.
In most cases you cannot do "reverse lookup" on tax id in the US. You can verify, but for that you need to have more than just the FEIN/SSN. You should also have a name, and some times address.
Non-profits, specifically, have to publish their EIN to donors, so it may be easier than others to identify those. Other businesses may not be as easy to find just by EIN.
If the organization is a non-profit. You can search by EIN on Charity Navigator's website FOR FREE. https://www.charitynavigator.org/