The article argues that both administrative and criminal tools are necessary for the protection of EU financial interests and that the mechanisms of cooperation between OLAF and the EPPO are suitable to foster a functioning collaboration. However, criticisms still emerge, both on the functioning of OLAF, and as regards operational activities of the EPPO and its cooperation with national prosecutors. Guarantees for private parties involved in administrative and criminal investigations cannot be ignored, and several shortcomings in the system of judicial protection need to be addressed. Effectiveness of the system and protection of guarantees should not be considered separate, especially in the context of the challenges that Next Generation EU (NGEU) raises for the protection of EU financial interests. Guarantees such as legal certainty and independence of the judiciary, are basic tenets of the rule of law, which, as set out in the Conditionality Regulation and further clarified by the ECJ, is in itself a condition for effectively protecting EU financial interests.