Most psychological studies on tax behaviour concentrate on income tax and determinants of compliance. The more tax knowledge possessed by taxpayers, the more positive these taxpayers' attitudes, the higher their ethical beliefs, the stronger their social norms and conviction of a fair tax system, and the stronger the deterrence in terms of audits and sanctions of evasion (e.g., Webley, 2004). Also, perceived opportunities not to comply determine tax behaviour. However, opportunities vary considerably and are definitely higher among the self-employed and entrepreneurs.

Opportunity to evade was found to be the most probable and relevant determinant of non-compliance (e.g., Antonides and Robben, 1995; Groenland and van Veldhoven, 1983; King and Sheffrin, 2002; Lewis, 1982; Robben et al., 1990b; Slemrod, Blumenthal and Christian, 2001; Vogel, 1974; Wallschutzky, 1984; Webley et al., 1991). It can be expected, therefore, that the self-employed and entrepreneurs are more prone to tax evasion than employed people earning a salary. Also, cash economy activity is more prevalent among the self-employed. On the other hand, Ahmed and Braithwaite (2005) argue that a number of studies have described small-business owners as law-abiding, responsible and ethical, and as taking their tax obligations seriously (e.g., Brown, 1985; Cunningham and Lischeron, 1991). Moreover, their personal characteristics have been portrayed as ambitious, hard-working, courageous and individualistic (C. J. Collins, Hanges and Locke, 2004; DeCarlo and Lyons, 1979; Verheul, Uhlaner and Thurik, 2005).