Chaplin v Commissioner of Taxes (SA)

The High Court of Australia considered a dispute between Chaplin, the taxpayer, and the Commissioner of Taxes (SA). The core of the disagreement concerned the Commissioner's assessment of income tax on the salary earned by the taxpayer, who was an officer of the Commonwealth. The taxpayer contended that his salary was not subject to State taxation.

The central legal issue before the High Court was whether the Parliament of South Australia possessed the legislative power to impose a tax on the salary of a Commonwealth officer, notwithstanding any potential implications arising from the Commonwealth's own legislative authority. This involved an examination of the constitutional division of powers between the Commonwealth and the States, particularly in relation to taxation.

The Court's reasoning focused on the principle of mutual non-interference between the Commonwealth and the States in the exercise of their respective constitutional functions. It was held that the Commonwealth Parliament had, by enacting legislation granting the States authority to tax Commonwealth officers, effectively removed any constitutional impediment to such taxation. Consequently, the State of South Australia was empowered to levy tax on the salary of a Commonwealth officer. The appeal was dismissed.