Advance ruling defines binding written decisions on proposed or ongoing supplies, available to registered or prospective taxpayers. An advance ruling is a written decision by the Authority or the Appellate Authority on specified questions relating to the supply of goods and/or services proposed or undertaken by an applicant. 'Applicant' means any person registered or seeking registration under the Act, and 'application' refers to an application to the Authority under the relevant provision. The Authority and Appellate Authority are the bodies constituted to issue and to hear appeals of such rulings.