Transitional GST provisions govern refunds, pre-existing claims, contract supplies, and avoidance of double taxation under the new regime. Miscellaneous transitional provisions govern returned goods, price revisions, refund claims, appeals, assessments, revised returns, and supplies under pre-appointed-day contracts. They preserve the application of the existing law for pending or pre-existing claims and proceedings, provide for cash refunds where admissible, and require recovery as arrears of tax under this Act where amounts become recoverable. The provisions also address avoidance of double taxation, goods sent on approval, tax deducted at source before the appointed day, and credit for value added tax or service tax paid under the existing law.