Modification of advance rulings: Authority may alter rulings for mistakes of law or fact after hearing affected parties. The Authority for Advance Rulings may modify an order or advance ruling suo motu or on petition by the applicant or the Principal Commissioner or Commissioner, before pronouncement or before the ruling has been given effect, if satisfied the ruling was pronounced under a mistake of law or fact, and may make appropriate modifications after allowing the applicant and the Principal Commissioner or Commissioner a reasonable opportunity of being heard.