Croatian Transmission System Operator (hereinafter: HOPS) as a member of ENTSO-E participates in the ITC (English "Inter Transmission System Operator Compensation"; hereinafter: ITC mechanism) mechanism and therefore, on a monthly basis, analyzes the losses caused by transit through its power grid. Losses caused by transit have a positive sign if neighboring and sometimes more distant TSOs affected the power flows on the HOPS transmission lines, while they have a negative sign if the HOPS affected the power flows of other TSOs. The paper describes the ITC mechanism in general, analyzes the impact of transit on power flows through transmission lines and the resulting losses, as well as the impact of topology changes on losses due to transit. Every electric power system connected in an interconnection, in addition to the planned import or export of electricity for its own needs, also transmits certain amounts of electricity due to transit that cause losses in its transmission network. The ITC mechanism is designed in a such way that is based on the input data (realized cross-border exchange, network topology and losses, vertical load of the system), it is determined which participants must pay compensation for the losses caused to participants. Each TSO submits the total system load on the transmission network, the cost of losses, details of capacity allocations that do not comply with the congestion management guidelines. Each party can check data from other ITC parties, and each TSO is obliged to submit six snapshots once a month no later than 10 days after each accounting month. Snapshot is a snapshot of the state of the power network which contains the network topology, aggregates, loads that were on the network at a given moment and the model of the 400 and 220 kV network. For the ITC calculation, the third Wednesday of the month and the previous Sunday, files 03:30, 11:30 and 19:30 are taken and the mentioned files are approximated to the whole month. Based on the data submitted through the ITC mechanism an individual TSO can receive money, but also pay to another TSO. As a rule, if the TSO is a large importer or exporter and causes congestion in the network of another TSO then it pays. The TSO that transits energy through its network, as a rule creates greater losses which means that it receives compensation through the ITC mechanism. The ITC mechanism has a complex calculation that includes the difference of active power losses, cost of losses, WWT compensation and Final Net Position II. The ITC mechanism represents a black box with many inputs and outputs where each operator within the RG CE pays or receives money and the sum of money at the end must be equal to zero.