substantially modified system
as defined in Directive (EU) 2019/520 of the European Parliament and of the Council of 19…, Article 2, point (19) (Definitions)
an existing electronic road toll system that has undergone or undergoes a change which requires EETS providers to make modifications to the interoperability constituents that are in operation, such as reprogramming or adapting the interfaces of their back office, to such an extent that re-accreditation is required;