Purpose: Tackling large informal economies is particularly challenging due to their self-perpetuating nature and complex participatory motivations. This thesis reveals the strongest determinants of business tax evasion, suggesting new evidence for more adequate policy approaches. Literature: The institutional asymmetry paradigm (IAP), adopted in this study, poses specific empirical challenges. Indeed, how to measure empirically the intrinsic circularity between tangible and intangible phenomena, affecting tax evasive behaviour. The contribution to the literature debates is through appraisal of these issues, proposing an economic model of partly informal entrepreneurship. Research aims: The main research aim is to develop a holistic account of the socio-economic influencers of the processes of tax evasion and (in)formalisation. A comprehensive review of tax policy management has been conducted, exposing the three major environmental pressures (institutional, economic and political) on Bulgaria's National Revenue Agency (NRA). It has been studied how institutional quality, procedural fairness and distributive justice transform into tangible economic effects on small businesses' evasive behaviour. Methodology: Mixed methods in exploratory sequential design. The in-depth semi-structured interviews with key NRA officials have been supplementary analysed with NVivo and IBM SPSS Modeler for increased findings' objectivity. This informed a quantitative questionnaire to investigate entrepreneurs' informal tactics. Utilising proven multi-disciplinary methods (Decision trees, Neural and Bayesian networks), the study advances an innovative predictive socio-economic profiling of business tax evaders. Findings and contributions: Operating in the most challenging EU economic environment, Bulgaria's NRA experiences political influence for asymmetrical tax gap closure, which leads to unjustifiable regulative formalism within an outdated deterrence orientated approach. 76.5% of the entrepreneurs evade taxes due to unfair competition ensuing survivalist reasoning. Evidently, the informal economy share is much higher than current macro-measurement methods report (31.2% of GDP). These tough policy challenges could be tackled only through inducing financially and socially efficient voluntary tax compliance.