In both the UK and Poland, tax avoidance in personal service provision is a significant problem. Workers in this area, often termed ‘Friday-to-Monday contractors’, obtain tax advantages by supplying their services via intermediaries or through the operation of other accessible legal forms. In the UK, the controversial tax legislation colloquially referred to as IR35, has particularly affected the IT industry by significantly reducing the tax benefits for contractors who provide their services through a personal service company. By contrast, in Poland, individuals have an option to register as ‘entrepreneurs’ thereby maintaining their self-employment status. This offers considerable tax concessions in comparison with employment. This book considers how tax authorities in the two countries have tackled these forms of tax avoidance by conferring quasi-employment status on individuals who would be regarded as employees had it not been for these intermediaries. The book should be especially useful to professional contractors, intermediaries, agencies and their tax advisers.