Unjust enrichment did not bar refund where duty incidence stayed with the supplier and was not passed to the buyer.

Refund was not barred by unjust enrichment where cylinders were supplied at a provisional price, duty was paid on that basis, and the purchaser later reduced the price and adjusted the excess, including duty, against later supplies. On those facts, the incidence of duty was not passed on to the buyer and was borne in substance by the supplier, so the refund claim was maintainable.

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Issues: Whether the refund claim was barred by the principle of unjust enrichment.

Analysis: The respondents had supplied cylinders at a provisional price, paid duty on that basis, and the purchaser subsequently reduced the price and adjusted the excess amount, including duty, against later supplies. On these facts, the incidence of duty was not passed on to the buyer and was in substance borne by the respondents.

Conclusion: The principle of unjust enrichment was not attracted and the refund claim was not barred on that ground.

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