Commission Delegated Regulation (EU) 2016/957 does not explicitly specify whether the annual audit should be external or internal. Therefore, Persons Professionally Arranging or Executing Transactions (PPAETs) and trading venues may conduct the required annual audit either internally or externally. If it is carried out internally, the audit is expected to be performed by an independent function. It is also worth noting that the reference to an internal review should be understood as a complementary exercise to the audit.