Determination of Optimal Value Added Tax Rate Based on the Size of Underground Economy

Nowadays it is obvious that higher share of tax revenues in budgeting and its role in developing dynamic economy has been a main criterion of growth in each country. The value added tax has been focused by policy makers due to its transparent collection. It is crucial to determine optimal and appropriate tax rates to achieve economic objectives. The underground economy and its activities which are accompanied by false information declaration affect the level of government tax revenue collections. This paper seeks to determine optimal tax rates in three introduced models by using the Particle Swarm Optimization (PSO) Algorithm and the current data during the period 2008-2017 in two different conditions of underground economy and its absence. The results indicate that government collects near optimal value added tax by VAT rate optimization. On the other hand, the higher changes in value added tax rates have significantly positive effect on underground economy.