This article discusses the existence and development of informal judicial practices in the Belgian legal order. It starts with the observation that the Belgian legal system is already highly formalized and suggests two reasons for that. Further, it shows that despite this rather high degree of existing formalization, important informal practices have nevertheless taken shape. However, over time the legislature intervenes, often as a reaction to some kind of external catalyst, and formalizes those previously informal aspects of the Belgian judicial system. This article therefore describes the Belgian legal order as a process of incremental and reactive formalization, taking place between the judiciary and the legislature. ; This article discusses the existence and development of informal judicial practices in the Belgian legal order. It starts with the observation that the Belgian legal system is already highly formalized and suggests two reasons for that. Further, it shows that despite this rather high degree of existing formalization, important informal practices have nevertheless taken shape. However, over time the legislature intervenes, often as a reaction to some kind of external catalyst, and formalizes those previously informal aspects of the Belgian judicial system. This article therefore describes the Belgian legal order as a process of incremental and reactive formalization, taking place between the judiciary and the legislature.