Voidability of advance rulings: can be declared void ab initio if obtained by fraud or suppression, subject to hearing. Authority may declare an advance ruling void ab initio if procured by fraud, suppression of material facts, or misrepresentation, subject to giving the applicant or appellant an opportunity to be heard; the ruling's legal effect is nullified and the period from the ruling to the voiding order is excluded for computation of specified limitation periods, and the order must be sent to the applicant, the concerned officer and the jurisdictional officer.