(4)Third-country external reviewers can offer services under Regulation (EU) 2023/2631 on the basis of registration based on an equivalence regime, on the basis of recognition, or on the basis of the authorisation of an endorsement by an external reviewer established in the Union that is registered with ESMA. The fees to be paid to ESMA should reflect the different extent of supervisory effort and hence cost associated with each of these options. The fees for third-country external reviewers applying for registration under an equivalence regime should thus take into account the lower supervisory effort and cost as they are already registered and thus assessed and supervised in a third country. Third-country external reviewers applying for recognition should pay the same fee as Union based external reviewers to reflect the fact that the supervisory effort and cost are the same.