Promissory estoppel cannot bar retrospective tax validation, and a retrospective levy is not unconstitutional unless confiscatory.

Promissory estoppel cannot be used to prevent a legislature from enacting or validating retrospective tax law where an exemption had earlier been granted by subordinate notification. The article also states that a retrospective tax does not become unconstitutional merely because it is retrospective; invalidity arises only if the burden is shown to be confiscatory or an unreasonable restriction on business rights, or otherwise contrary to constitutional guarantees. On the stated facts, the validating sales tax was treated as a statutory intervention, not an enforceable executive promise, and the levy was not shown to be so excessive as to destroy its character as a tax.

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Issues: (i) Whether the doctrine of promissory estoppel could be invoked to invalidate a validating statute which retrospectively imposed sales tax on exercise books; (ii) Whether the retrospective levy was confiscatory or otherwise imposed an unreasonable restriction on the right to carry on business under Articles 19(1)(f) and 19(1)(g) of the Constitution, or violated Article 31.

Issue (i): Whether the doctrine of promissory estoppel could be invoked to invalidate a validating statute which retrospectively imposed sales tax on exercise books.

Analysis: The exemption granted in 1973 was created by subordinate notifications issued under the Sales Tax Act. The 1976 amending statute did not merely operate through the executive notifications; it altered the relevant entries by legislative enactment and validated the levy retrospectively. Promissory estoppel cannot bar the exercise of legislative power, and it cannot be used to compel the legislature to maintain an exemption once the law is changed. The levy therefore rested on statutory intervention, not on any enforceable executive promise.

Conclusion: The doctrine of promissory estoppel did not invalidate the amending Act.

Issue (ii): Whether the retrospective levy was confiscatory or otherwise imposed an unreasonable restriction on the right to carry on business under Articles 19(1)(f) and 19(1)(g) of the Constitution, or violated Article 31.

Analysis: The levy was retrospective for a limited period and operated as a validating measure. The scheme also reduced hardship by exempting paper and permitting adjustment of tax already borne on raw material. Retrospective tax legislation is not per se confiscatory, and inability to pass on tax does not by itself render a taxing statute unconstitutional. On the facts, the burden was not shown to be extortionate or so excessive as to destroy the character of the tax as a tax.

Conclusion: The amending Act was neither confiscatory nor unconstitutional under Articles 19(1)(f), 19(1)(g), or 31.

Final Conclusion: The constitutional challenges failed, and the writ petitions were dismissed with costs.

Ratio Decidendi: Promissory estoppel cannot be invoked to restrain a legislature from enacting or validating a tax law, and a retrospective validating tax will not be struck down merely because it is retrospective unless it is shown to be confiscatory or otherwise constitutionally unreasonable.

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