This article addresses fiscal policy as a key instrument for promoting the transition to a circular economy. It is based on the hypotheses that (1) the current tax system penalizes circular activities, which are generally labour intensive, as opposed to new product manufacturing activities, which are generally intensive in materials and energy, highly automated and robotized, and (2) that the environmental taxation implemented in recent decades is unable to introduce significant changes to stop climate change or keep the economy within planetary ecological limits. This article examines the basis of an alternative tax system and tax instruments for correcting the current linear economy bias and driving the transition to a circular economy. Proposals are developed for both structural and partial reforms of the fiscal system, focusing on tax measures that can be implemented in the medium or short term to boost a circular economy. More specifically, we suggest a complete redesign of the currently opaque and significant amount of tax expenditure to transform environmentally harmful tax benefits into environmentally friendly tax measures that are suitable for the circular economy.