This article analyzes the modified form of ad valorem royalty recently announced by the WA government in relation to gold production, which features a threshold price below which there is no tax liability and compares this royalty with a profit-based royalty. The level at which the threshold price is set plays an important role in determining the performance of the royalty in relation to its impact on production and the expected level and variability of tax revenue. It is argued that the higher this price is set, the stronger the grounds for preferring a profit-based royalty, eve taking into account the reliability of each form for generating tax revenue.