enforcement of compliance over a span of several years. Fraud charges have resulted in the highest conviction rate of all cases brought by the IRS against tax offenders. The IRS encourages people to report tax fraud. To report tax fraud you may adopt one of several modes of action. The IRS has a specific form letter. 3949-A is the required document. You can also, however, send a letter to the appropriate authorities - municipal, county, state or federal, containing the appropriate information. You may or may not identify who you are. It is your personal preference.