Chapter 7: The Multifaceted Role of Constitutional Courts in Applying the Ability to Pay Principle: A Comparative Analysis of the DACH, Italian and Spanish Jurisdictions

This chapter examines how the constitutional courts of Austria, Germany, Italy, Spain and Switzerland apply the ability to pay principle (Leistungsfähigkeit, capacità contributiva, capacidad económica). Adopting a contextualist comparative method and a “most similar cases” design, it reads each court’s case law reasoning against the constitutional text, the position of the principle within the wider order, and the federal or unitary structure of the state. The analysis reveals a layered pattern: near-complete convergence on premises – all five courts treat the principle as indeterminate and defer to the legislature in selecting the taxable event – alongside systematic divergence in doctrinal technique, from the Austrian variable-intensity scrutiny to the German Folgerichtigkeitsgebot, the Italian coerenza interna test, the Spanish IIVTNU jurisprudence and the Swiss holistic tariff review. Beneath this divergence lies a shared structural tendency: every court polices the internal coherence of a tax more readily than it imposes external substantive standards. The common meaning of ability to pay is thus structural, not substantive.