(4)The annual supervisory fee charged by ESMA to CTPs should, as a general rule, cover all activities carried out in connection with their supervision. For that purpose, each year, ESMA should assess the direct and indirect supervisory costs in relation to CTPs, including the cost for ESMA’s staff that is directly allocated to supervisory tasks and the cost of horizontal services, such as the cost for the operational and administrative support provided to staff that is directly involved in supervisory tasks. Such assessment should enable ESMA to charge each individual CTP a fee that covers those costs and is proportionate to its revenue compared to the total revenue of all CTPs. A CTP’s revenue that is related to activities that are directly ancillary to core services should be included in the calculation of the applicable turnover if it is likely to have an impact on ESMA supervision of that CTP and is not already covered by separate supervision activities. To match ESMA’s estimated supervisory costs, the annual supervisory fees should be adjusted every year. Fees for ESMA’s supervisory activities carried out in connection with CTPs should be set at a level such as to avoid a deficit or a significant accumulation of a surplus. Where there is a recurrent deficit or surplus, the level of fees should be revised.