Every year, the Commission submits, in line with Protocol No 2 to the Treaties, a report on the application of the principles of subsidiarity and proportionality. Since 2005, the Commission also publishes an annual report on its relations with national Parliaments. Given the important role that national Parliaments play in monitoring the application of the principles of subsidiarity and proportionality, the Commission decided to merge both reports in 2018.
https://ec.europa.eu/info/node/93413
https://ec.europa.eu/info/node/55953
https://ec.europa.eu/info/node/55956
https://ec.europa.eu/info/node/55957
https://ec.europa.eu/info/node/55959
https://ec.europa.eu/info/node/55963
https://ec.europa.eu/info/node/55960
https://ec.europa.eu/info/node/55968
https://ec.europa.eu/info/node/55974
https://ec.europa.eu/info/node/55976
https://ec.europa.eu/info/node/55978