This study examines the impact of alternative designs of the Spanish Wealth Tax using fiscal microsimulation techniques based on administrative microdata from the Spanish Tax Agency’s Household Panel. We compare the current structure of the tax with eight simulated scenarios that either modify key parameters such as exemption threshold, regional deductions, and tax base or simulate real designs inspired in the Norwegian, Swiss or French wealth taxes and in a scheme proposed by Piketty (2014). By isolating the effects of each potential reform, we assess how different designs affect progressivity, revenue, redistributive capacity, taxpayers’ characteristics and long-run net wealth inequality. Results show that various alternative scenarios have the potential to increase tax progressivity, redistributive capacity and the decrease of long-run net wealth inequality. Overall, our findings offer robust empirical evidence to inform policy discussions on the role of wealth taxation in promoting equity, efficiency, and fiscal sufficiency in Spain.