(4)It is important to ensure appropriate authorisation and supervision of a CSD. As such, a list of the relevant authorities issuing the most relevant Union currencies in which settlement takes place to be involved in the process of authorisation and supervision of a CSD should be defined. This should be based on the share of the currencies that those authorities issue in the total value of settlement instructions against payment settled annually by a CSD and on the share of settlement instructions against payment settled by a CSD in a Union currency compared to the total value of settlement instructions against payment settled in that currency across all CSDs in the Union.