Recent policy discussion has highlighted the variety of ways in which the world of work is changing. One development prevalent in some countries has been an increase certain forms of non-standard work. Is this beneficial, representing increased flexibility in the workforce, or detrimental, representing a deterioration in job quality driven by automation, globalisation and the market power of large employers? These changes also raise crucial issues for tax systems. Differences in tax treatment across employment forms may create tax arbitrage opportunities. This paper investigates the potential for such opportunities for eight countries. It models the labour income taxation, inclusive of social contributions, of standard employees and then of self-employed workers (with applicable tax rules detailed in the paper’s annex). The aim is to understand whether countries’ tax systems treat different employment forms differently, before approaching the broader question of whether differential treatment has merit when evaluated against tax design principles.