A large body of literature has examined the impact of the horizontal market structure on the tax incidence on consumers. However, the extent to which the vertical market structure affects the tax pass-through —which might be particularly relevant in the presence of the double marginalisation problem— is an unexplored question. Using a confidential dataset of gas station contracts with a major Spanish refiner, in combination with their retail fuel prices and characteristics, we document that the pass-through of a tax onto prices is about 38 percent higher in vertically-integrated gas stations than in independent ones. Our estimates allow us to assess the impact on government revenue and emissions under different counterfactual market scenarios.