When Does the EPPO Investigate EU Fraud? Explaining the Enforcement Gap in Supranational Prosecution

The European Public Prosecutor’s Office (EPPO) was established to address long-standing deficiencies in the prosecution of crimes against the EU’s financial interests. Despite its hybrid design and supranational mandate, early operations have revealed notable cross-national disparities in enforcement outcomes. If reported violations are not systematically pursued, potential offenders may calculate that non-compliance carries minimal risk (Hafner-Burton & Schneider, 2019), while whistleblowers might hesitate to report suspected fraud due to the low likelihood of investigations. This study thus offers the first systematic and comparative assessment of the EPPO’s enforcement actions, examining why the proportion of reported offences leading to formal investigations varies across member states. Using fuzzy-set Qualitative Comparative Analysis (fsQCA), it tests a range of conditions, including legal alignment, administrative capacity, national cooperation, prosecutorial independence, and judicial receptiveness, to identify the combinations that enable or constrain the EPPO’s investigatory activity. Findings complement explanations of how institutional designs shape enforcement outcomes, while identifying the roots of variation can inform reforms to strengthen EU anti-fraud mechanisms in a context where 71% of citizens perceive corruption as endemic (Pérez-Gabaldón et al., 2025).