The Taipei office of the NTA says that it has to verify these kinds of claims. To do so, it usually sends an investigator to look in on the business at different times of day. When it finds a snack stand that really is generating business beyond its assessment level, it levies a supplemental tax on the excess.
財政部台北國稅局表示，民眾的「爆料」必須經過查證，通常國稅局會在「不同時段前去站崗」，若發現生意好的小吃攤營業額確實超過標準，超過的部分就要補稅。