Transitional GST provisions clarify refunds, credit carry forward, and treatment of pre appointment contracts and returns under new law. Transitional rules address refunds, credit treatment and taxability for transactions spanning the appointed day. Returned goods on which duty was paid under the existing law are refundable if returned within six months by unregistered persons, while returns by registered persons are deemed supplies. Pre appointed contracts with upward price revisions require supplementary invoices treated as outward supplies; downward revisions permit credit notes, with supplier relief contingent on recipient reduction of input tax credit. Proceedings and refund claims under existing law are to be disposed under that law, refunding admissible amounts in cash and treating unrecovered liabilities as arrears under this Act, not admissible as input tax credit.