(a) where in pursuance of an assessment or adjudication proceedings instituted, whether before, on or after the appointed day, under the existing law, any amount of tax, interest, fine or penalty becomes recoverable from the person, the same shall, unless recovered under the existing law, be recovered as an arrear of tax under this Act and the amount so recovered shall not be admissible as input tax credit under this Act;
(b) where in pursuance of an assessment or adjudication proceedings instituted, whether before, on or after the appointed day, under the existing law, any amount of tax, interest, fine or penalty becomes refundable to the taxable person, the same shall be refunded to him in cash under the said law, notwithstanding anything to the contrary contained in the said 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.