If you suspect a company or individual of tax fraud, you can report it to the IRS by completing a Form 3949-A. The IRS does not require that you identify yourself when reporting tax fraud, but it is helpful and they will work with your regarding confidentiality if that is a concern of yours.
Tax law in the U.S. applies to all persons, businesses and entities who make money. If you make money, you pay taxes, and those monies are used to run the government and pay for community programs that benefit every person. The temptation to avoid taxes that are legal obligations may seem natural, but it is unethical and illegal. The cost of not paying taxes by fraudulent means is not worth the short term savings. If you don't get caught at first, it will leave you in fear of losing everything.
An attorney can help you remain confidential and avoid potential legal action by acting on your behalf, giving you advice about delicate legal situations and advising you of the law and how to comply with it. Because attorneys work with the legal system daily, they know the ins and outs and can easily navigate the system.