Except in the case of fraud, intent to evade this chapter or rules and regulations adopted to implement this chapter, or failure to file a return, the notice of a deficiency determination shall be mailed within three years after the amount that is proposed to be determined was due or within three years after the return is filed, whichever period expires later. In the case of failure to file a return, the notice of determination shall be mailed within eight years after the amount that is proposed to be determined was due.