The two phenomena of financial corruption and the underground economy are closely related to each other, so that the existence of the underground economy provides the possibility of creating financial corruption. Considering the increase in inflation and the decrease in per capita income and the almost increasing trend in the tax burden, it can be acknowledged that the increase in the tax burden has been effective on the increasing trend of the relative size of the underground economy. Also, the unemployment rate has a direct effect on the underground economy, but in terms of size, the unemployment rate is less elastic than the tax burden, therefore, due to the high elasticity of the underground economy to the tax burden, the government should have a suitable combination of tax components according to Also, the government should take effective steps to fight against corruption and tax evasion.