In this paper, we analyze a tax on sugar-sweetened beverages (SSB) that was introduced in Catalonia on May 1, 2017. The Bill established the requirement of a 100% pass-through of the tax to the final consumer and two levels of the tax: 0.08 euro/liter for products with 5-less than 8 g of sugar and 0.12 euro/liter for products with 8 g of sugar or more. Previous literature focusing on the impact of SSB taxes finds that pass-though is only complete in the long-term. Our paper provides new evidence that, when the tax increases prices substantially and immediately, the sales response is also significant. In particular, we estimate that the new SSB tax in Catalonia reduced SSB purchases by 7.7%. We document that part of this reduction is substituted by an increase in sales of zero/light drinks (substitution effect). Importantly, the reduction in purchases is stronger in areas with a higher incidence of obesity, in areas with higher household incomes and for products with higher sugar content. (C) 2019 Elsevier B.V. All rights reserved.