your questions touch very sensitive issues that you really need to discuss in private with an attorney.
Some issues and agencies prior of giving info need to provide you with immunity for some issues
There are tax fraud, govermental fraud, healthcare fraud and plethora of other issues that can be applied as per case and facts.
You need a lawyer that is a fraud examiner and knows about fraud to help you
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I'm trying to figure out your question. If you are still employed by the company you may get protection for reporting illegal activities to governmental agencies. If you are no longer working for the company and you want to report illegal activity then you should talk to an employment law attorney.
As a practical matter, you should be able to get much of the information you are seeking from the IRS website. My understand is the IRS offers rewards under certain circumstances and again the information should be available on the IRS website.