South Australia v Commonwealth ("the First Uniform Tax case")[1] is a decision of the High Court of Australia that established the Commonwealth government's ability to impose a scheme of uniform income tax across the country and displace the State.

The High Court held the laws were valid, despite the practical result being the inability of the states to impose income tax.

Hence the Commonwealth can do such things to encourage or discourage a state from exercising its powers, which are technically not coercion.

The Income Tax (Wartime Arrangements) Act 1942,[5] was upheld by a majority under the defence power.

The decision in relation to section 221 of the Income Assessment Act 1942 was subsequently overturned by the High Court in the Second Uniform Tax case.