This study provides a comprehensive analysis of the enforcement of fines and pecuniary obligations imposed by the ECB within the Eurosystem and the Single Supervisory Mechanism (SSM) under Art. 299 TFEU – an issue which has, to date, been treated only rudimentarily in literature/judicature. The focus in Part I lies on five categories of monetary obligations that the ECB may levy. Against the background of these case groups, the European law requirements that exist for enforcement will be shown. Part II will show how these requirements are fulfilled in euro and non-euro Member States (MSs). The latter will be based on a comparative analysis of the respective data collected in 2020 via a questionnaire survey in 21 MSs. The relevance of the findings are, however, not limited to the ECB. Legal acts of the Council and the EC However, not the EP, see ECJ, 6 July 2017, Gollnisch v Parliament, C-189/17 P(R), ECLI:EU:C:2017:528, para 46; Matthias Ruffert, in: Christian Callies/Matthias Ruffert (eds.), EUV/AEUV, Das Verfassungsrecht der Europäischen Union mit Europäischer Grundrechtecharta, 5th edn., 2016, art. 299 mn. 1; differing Maria Geismann, in: Hans von der Groeben/Jürgen Schwarze/Armin Hatje (eds.), Europäisches Unionsrecht, 7th edn., 2015, art. 299 mn. 2; Martin Gellermann, in: Rudolf Streinz (ed.), EUV/AEUV, Vertrag über die Europäische Union, Vertrag über die Arbeitsweise der Europäischen Union, Charta der Grundrechte der Europäischen Union, 3rd edn. 2018, art. 299 mn. 4. , as well as judgments of the CJEU (Art. 280 TFEU), are enforced under the same regime; Art. 82 of the Agreement on a Unified Patent Court (UPCA) Council Agreement on a Unified Patent Court [2013] OJ C175/1, not yet in force; see also Treaty Establishing the European Atomic Energy Community [2012] OJ C327/1, art. 164 which is almost identical to TFEU, art. 299. is modelled on Art. 299 TFEU.