Non-refund of tax in certain cases

33BB. Non-refund of tax in certain cases. 33BB. Where a levy and collection of tax is held invalid by any judgement or order of a court or Tribunal, it shall not be necessary to refund any such tax to the dealer unless it is proved by the dealer to the satisfaction of the assessing authority that the tax has not been collected from the purchaser: Provided that where any court or Tribunal holds the levy and collection of tax as invalid and orders refund of any tax collected, the refund shall be restricted to the period of three years immediately preceding the judgement or order.