Transitional GST provisions govern refunds, input tax credit carryforward and recovery for pre-appointment transactions. Transitional GST provisions govern refunds, credit treatment and recovery for transactions spanning the appointed day: identifiable returns of goods taxed under the previous law may yield refunds; contractual price revisions after the appointed day necessitate supplementary invoices or permit credit notes that adjust tax only if recipients reduce their input tax credit; claims, appeals and assessments initiated under the prior law are to be disposed under that law with refunds paid in cash but rejections and prior reversals not admissible as input tax credit under the new Act.