The first report outlines the reasons why international tax avoidance and evasion through the use of tax havens is a concern to the tax authorities of OECD Member countries and examines measures introduced to combat such use. The second report sets out the problems posed for tax administrations by the fact that their resident taxpayers make use of base companies (generally subsidiary companies) in tax havens to shelter there income derived from source countries (which may in some cases be the residence country itself) and in that way to escape tax normally payable to the country of residence. The third report deals with the problems created for tax authorities in source countries by the mechanism of "treaty shopping". The final report deals with taxation and the abuse of bank secrecy.