All the empirical evidence indicates that the Netherlands is a tax haven. This is because it deliberately offers companies who would not otherwise seek to be resident within its territory the means to reduce their tax charges on interest, royalties, dividend and capital gains income from foreign subsidiaries. This SOMO report investigates the extent to which the Netherlands can be regarded as a tax haven, and analyses the factors behind this, such as the unique network of bilateral treaties for the avoidance of double taxation and the special fiscal regimes for group financing operations. It estimates the number of ‘mailbox companies’, mostly established to route financial lows through the Netherlands purely for fiscal reasons, at almost 20,000, and this number has been increasing rapidly in recent years.