This paper is an excerpt and a comprehensive research on Non-Technical losses during T & D. In developing countries, the utility companies are finding it difficult to address losses due to theft, meter tampering and allied problems which affect the quality of supply, increase on generation load and has a significant economic impact on the functioning of the utility company and its genuine consumers in the form of an excessive tariff. As the single largest contributor to T & D losses, various aspects and methods used for theft and detection mechanisms are discussed. This article also highlights the components of AMI and how a simple method of two smart meters equipped with harmonic generators could be used in conjunction to detect theft.