This paper attempts to estimate and evaluate a performance of the tax system in Libya during the time period (1994-2019), by estimating tax performance indicators such as tax capacity, tax burden, tax effort, and income elasticity.An ARDL model is used to estimate the tax capacity function. Results show that there is a sharp decline in all indicators of tax performance, which means inefficient performance of the tax system in Libya during that period. In other words, the inelasticity of the tax system and the ineffectiveness of its policies have caused the tax energy not to be utilized in a way that can collect the largest amount of money needed to accelerate the process of economic- social development in the country.