This leaflet describes the procedures and structures for cost accounting and allocation between RUs as part of the logistical optimisation of the use of RU-kept wagons in international jointly-operated traffic, known as the LOWCOST system. This leaflet does not regulate the level of applicable charges, penalties, etc. These are the object of additional individual agreements between the railways concerned in the use of the wagon. The following recommendations promote a consistent implementation of the principles defined in the LOWCOST system, in line with COTIF 99, the General Contract for the Use of wagons (GCU) and EU Directives. This leaflet provides a universally valid framework, recommended for those RUs that use freight wagons kept by RUs, to close the gaps in the GCU regulations and simultaneously keep the handling and processing costs to an absolute minimum. The following recommendations are initially valid for bilateral traffic, pending the execution of more comprehensive studies on their wider application in traffic operated jointly by a greater number of carriers.