What is exchange of information? Exchange of information (EOI) between tax authorities has long been a key element of international co-operation in tax matters. More recently, however, growing levels of public and governmental concern regarding perceived tax avoidance (at both the individual and the corporate level) have caused the topic to assume a still greater significance, and have ensured that it has become a centrally important (and arguably more effective) cross-border anti-avoidance measure. There are a variety of different regimes and instruments pursuant to which tax authorities such as HMRC exchange information relating to taxpayers with overseas tax authorities. The primary focus of this Practice Note is the approach to EOI under double tax treaties or conventions (DTTs), although the other key platforms for EOI are also summarised. Most DTTs contain a specific provision dealing with EOI, which is often based on Article 26 of the Organisation for Economic Co-operation and Development (OECD) model tax convention (MTC). Under the terms of a DTT, information is typically exchanged for one of two purposes: