Transitional input tax credit rules govern refunds, credit/debit notes and recovery treatment across the appointed day. Transitional provisions treat returns, contractual price adjustments and cross regime credits at the appointed day. Returned goods sold within six months before the appointed day may yield refunds under the existing law when returned within six months, while registered-person returns are deemed supplies. Post appointed day upward price revisions require supplementary invoices or debit notes; downward revisions permit credit notes whose tax effect depends on recipient reduction of input tax credit. Proceedings pending under the existing law are to be disposed under that law, with recoverable amounts becoming arrears under this Act and not admissible as input tax credit; refunds are in cash under existing law. Agent entitlement to credit for principal's goods on hand is allowed subject to registration, stock declaration, invoice age and principal's non availment or reversal of credit.