In the context of deregulation, unbundling of utility services and open access of transmission facilities is becoming order of the day. In order to achieve transparency and fairness from the point of participants involved, it is necessary to get contributions from each generator (source) to loads, flows in the network and losses for the system. This paper attempts to evaluate real and reactive power flow in the network due to individual sources and its contribution to each load using the principle superposition which is fairly simple and straightforward. As a result, in a multilateral transaction environment, it is possible to fairly allocate charges for real and reactive power usage. In addition the extent of network loading by individual generator is computed which shows direction to manage network congestion in an effective manner. Sample system to illustrate the proposed approach and its implementation on a practical 72 bus Indian Southern grid equivalent 400/220kV network are presented.