This study investigates the optimality hypothesis of taxation and the volatility thereof in South Africa when using appropriate tax rates within a dynamic stochastic environment. Using a Marshallian macroeconomic model disaggregated by sectors (MMM-DA) several features of the South African economy are analysed that may contribute to the efficiency of the optimal taxation hypothesis. The results show that within a tax regime where revenue from labour and capital income constitutes the most significant source of government income, both such taxes distort the economy but that the distortion from a tax on capital exceeds that of a tax on income. This study has twofold implications. It highlights the impact of efficient optimal taxation on both overall economic growth and fiscal policy in the country.