Section 142(6)(a) in The Central Goods and Services Tax Act, 2017
(a)every proceeding of appeal, review or reference relating to a claim for CENVAT credit initiated whether before, on or after the appointed day under the existing law shall be disposed of in accordance with the provisions of existing law, and any amount of credit found to be admissible to the claimant shall be refunded to him in cash, notwithstanding anything to the contrary contained under the provisions of existing law other than the provisions of sub-section (2) of section 11B of the Central Excise Act, 1944 and the amount rejected, if any, shall not be admissible as input tax credit under this Act: