Domestic systemically important institutions (O-SIIs) are defined as those whose failure would have a significant impact on the financial system or the real economy. There are two main reasons for the imposition of additional capital requirements on such institutions:
- to reduce their probability of default, given the high economic and social costs this would entail;
- to ensure that they have a buffer that reflects the negative externalities their failure would generate.
An individual score for each bank
Systemically important institutions are identified using a methodology set by the European Banking Authority (EBA). This involves scoring each institution against quantitative indicators related to their size, complexity, interconnectedness and substitutability (the ability of other institutions to rapidly take over any critical services provided by the bank). In 2025, the application of this methodology resulted in the redesignation of eight Belgian institutions as O-SIIs: BNP Paribas Fortis, KBC Group, Euroclear Holding, ING Belgium, Belfius Bank, The Bank of New York Mellon, Investeringsmaatschappij Argenta and Crelan.
Capital buffers
For all of these O-SIIs, the NBB's Board of Directors has decided to maintain the capital buffers announced in 2023: 1.5% for BNP Paribas Fortis, KBC Group, Euroclear Holding, ING Belgium and Belfius Bank and 0.75% for The Bank of New York Mellon, Investeringsmaatschappij Argenta and Crelan.[1]
The O-SII buffers are primarily structural in nature. In the event of a persistent crisis and should the need for additional support arise, the funds can be released temporarily after coordination with the national and international authorities concerned. Release of these buffers would most likely be one of the last macroprudential tools to be used.
[1] Without prejudice to the caps laid down in Article 14 §5 of Annex IV to the Belgian Banking Act.