RTC § 7675

Except in the case of fraud, intent to evade this part or authorized rules and regulations, or failure to make a return, every notice of a deficiency determination shall be given to the supplier within three years after the last day of the month following the monthly period for which the amount is proposed to be determined or within three years after the return is filed, whichever period expires the later. In the case of a failure to make a return the notice of determination shall be served within eight years after the date the return was due.