Cash registers provide the key source of original information on the sales of goods and services in the retail sector needed to support tax reporting, payment and verification. In their efforts to improve compliance, reduce burdens and support honest taxpayers, tax administrations have made many attempts to ensure timely and uncompromised access to this source of information. Advances in digital technology have opened up new opportunities to reduce the tax risks that were traditionally associated with the vulnerability of cash register data. For some jurisdictions, the adoption of a specific type of electronic cash register, online cash registers connected to the tax administration’s systems, has been an important part of their compliance strategy. Drawing on the experiences and lessons learnt by a number of tax administrations, the goal of this report is to provide advice and guidance to tax administrations considering the adoption and implementation of online cash registers.