Retrospective tax withdrawal invalidates covered assessments, but refund remains subject to proof against unjust enrichment.

A retrospective withdrawal of mustard oil tax invalidated assessments made for the covered period, so the later assessment orders for periods ending 31 March 1993 and 30 June 1993 were unsustainable and were set aside. The earlier assessment order dated 6 January 1993 remained final because the appeal period under the repealed law had expired and no saved remedy survived. Any refund of tax paid was not automatic and was allowed only if the assessee proved that the tax burden had not been passed on to consumers, applying the doctrine of unjust enrichment.

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Issues: (i) Whether the assessment order dated 6 January 1993 had attained finality and could be interfered with in the later appeal and revision proceedings; (ii) Whether the assessment orders dated 27 December 1996 for the periods ending 31 March 1993 and 30 June 1993 were sustainable after the retrospective withdrawal of tax on mustard oil; (iii) Whether refund of tax paid for the latter two periods was barred unless the assessee established that the tax burden had not been passed on to consumers.

Issue (i): Whether the assessment order dated 6 January 1993 had attained finality and could be interfered with in the later appeal and revision proceedings.

Analysis: The assessment for the period ending 30 September 1992 was made when the levy on mustard oil was in force. The period for filing an appeal under the repealed sales tax law had expired long before the appeal was filed in 1998. In the absence of a pending or timely appeal, the saving provision in section 74 of the Assam General Sales Tax Act, 1993 did not preserve a remedy against that assessment order.

Conclusion: The assessment order dated 6 January 1993 was final and was not liable to be interfered with.

Issue (ii): Whether the assessment orders dated 27 December 1996 for the periods ending 31 March 1993 and 30 June 1993 were sustainable after the retrospective withdrawal of tax on mustard oil.

Analysis: The Assam Taxation Laws (Amendment) Ordinance, 1993 withdrew the levy on mustard oil with retrospective effect from 30 July 1992. By the time the impugned assessment orders were passed, the retrospective exemption governed the field. The Court also read the repeal and savings clause in section 74 of the Assam General Sales Tax Act, 1993 together with the earlier procedural provisions and held that the levy for those periods could not survive.

Conclusion: The assessment orders dated 27 December 1996 for the periods ending 31 March 1993 and 30 June 1993 were unsustainable and were set aside.

Issue (iii): Whether refund of tax paid for the latter two periods was barred unless the assessee established that the tax burden had not been passed on to consumers.

Analysis: Although the impugned assessments were quashed, the question of refund had to be tested on the principle of unjust enrichment. The assessee was required to establish that the burden of tax had not been passed on to third parties before any refund could be ordered.

Conclusion: Refund, if any, was made subject to proof that the tax burden had not been passed on to consumers.

Final Conclusion: The challenge succeeded only in part: the later assessment orders were annulled, the earlier assessment was left undisturbed, and any refund was conditioned on the doctrine of unjust enrichment.

Ratio Decidendi: A retrospective withdrawal of a tax levy will invalidate assessments made for the covered period, but refund of tax already paid remains subject to proof that the incidence of tax was not passed on to others.

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