Input tax credit eligibility: transitional conditions determine admissibility and refund mechanisms under GST law. Transitional input tax credit is admissible only if the amount qualifies as input tax credit, the registrant furnished all Central Excise and VAT returns for the six months prior to the appointed date, and the credit does not relate to goods sold under notifications claiming VAT refund; additionally, credits attributable to certain Central Sales Tax claims are ineligible for electronic credit unless substantiated as prescribed, though equivalent amounts will be refunded under the existing law when substantiation occurs.