The IRS maintains a tax fraud hotline recording at 800-829-0433, according to IRS.gov. This number is a recording, as the IRS does not accept alleged tax law violation referrals over the phone.
To report the fraudulent activity of an individual or business related to tax laws, you must complete IRS Form 3949-A, and mail the completed form to: Internal Revenue Service, Fresno, CA, 93888, explains IRS.gov. You may also send a letter to this address instead of completing Form 3949-A, but you must include the necessary information required by the IRS. If you suspect another type of fraud, such as someone stealing your identity or Social Security number, there are forms available to complete for these types of specific situations. If you receive fraudulent IRS emails or websites, the IRS has a Web page with information about phishing, through which you can report such activity.