Queensland Alumina Ltd v Alinta DQP Pty Ltd

The dispute in Queensland Alumina Ltd v Alinta DQP Pty Ltd was between an alumina refinery operator and a natural gas supplier, with the former claiming the latter underpaid them by failing to rebate excess payments. The matter was heard in the Queensland Court of Appeal, which was asked to determine whether there were inconsistencies in the contract terms that led to a shortfall in rebates. The central legal issues revolved around the interpretation of the contract, the impact of legislative changes on the agreement, the possibility of restitution for mistaken payments, and the applicability of estoppel by representation.

The court examined whether the Transportation Service Agreement (TSA) and the Access Principles contained within it were internally inconsistent, particularly regarding the currency of payments and the rate cap. It was found that the agreement's terms were not inconsistent and that the legislative changes did not alter the agreement. The court also determined that the appellant's payment of the excess amounts was not voluntary but rather due to a mistake. It held that the appellant was entitled to restitution for the mistaken payments that exceeded the maximum tariff. Furthermore, the court rejected the respondent's estoppel by representation claim, finding no clear and unambiguous representation had been made by the appellant.

The Court of Appeal allowed the appeal, setting aside the previous judgment in favour of the respondents and ordering a new judgment in favour of the appellant, with costs. The court directed that if the parties could not agree on the quantum of the judgment within 21 days, the issue should be remitted to the Trial Division for determination according to the court's reasons. This decision underscores the importance of careful contractual drafting and the consequences of failing to adhere to agreed terms.