All changes in the department of state revenue's interpretations of IC 6-4.1 that could increase a person's tax liability must be stated in rules promulgated under IC 4-22-2. In no event may a change in a departmental interpretation of IC 6-4.1 that could increase a person's tax liability take effect before the date on which it is promulgated in a rule.
IC 6-4.1-12-6.5