The taxes imposed by this chapter shall be assessed within three years from the date on which such taxes became due and payable. In the case of a false or fraudulent return with intent to evade payment of the taxes imposed by this chapter, or a failure to file a return, the taxes may be assessed, or a proceeding in court for the collection of such taxes may be begun without assessment, at any time within six years from such date. The Tax Commissioner shall not examine any person’s records beyond the three-year period of limitations unless he has reasonable evidence of fraud, or reasonable cause to believe that such person was required by law to file a return and failed to do so.