This paper contributes to the literature of public debt management by testing for tax smoothing behaviour in Indonesia. Tax smoothing means that the government smooths the tax rate across all future time periods to minimize the distortionary costs of taxation over time for a given path of government spending. In a stochastic economy with an incomplete bond market, tax smoothing implies that the tax rate approximates a random walk and changes in the tax rate are nearly unpredictable. For that purpose, two tests were performed. First, random walk behaviour of the tax rate was examined by undertaking unit root tests. The null hypothesis of unit root cannot be rejected, indicating that the tax rate is nonstationary and, hence, it follows a random walk. Second, the predictability of the tax rate was examined by regressing changes in the tax rate on its own lagged values and also on lagged values of changes in the goverment expenditure ratio, and growth of real output. They are found to be not significant in predicting changes in the tax rate. Taken together, the present evidence seems to be consistent with the tax smoothing, therefore provides support to this theory