The High Court of Australia has ruled in favour of the South Australian Treasurer in a dispute over the interpretation of the Casino Duty Agreement between SkyCity Adelaide and the state.

The court's judgment confirmed that credits on gaming machines, resulting from the conversion of loyalty points, should be included in gaming revenue for the purpose of calculating casino duty at the SkyCity Adelaide casino.

As a result, SkyCity Adelaide is now estimated to owe an additional A$10.3 million (NZ$11.4m) in casino duty, in addition to A$2.8m (NZ$3.1m) of additional duty.

The amount of interest payable on the outstanding duty, which is the subject of a cross-appeal by the Treasurer, will be determined by a single judge of the Supreme Court of South Australia at a later date.

If the decision is unfavourable to SkyCity Adelaide, it may be required to pay penalty interest of up to A$25.3m (NZ$27.9m).

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