Taxes are the second source of public revenues for the Libyan budget evasion leads to a reduction in these revenues. Libya, like other developing countries, suffers from the spread of this phenomenon, which has continental, legislative, economic, political, social, and other causes. Given the importance of the subject, the study aimed to identify the types of tax evasion in Libya and this phenomenon, while attempting to measure it. This was done using a set of financial economic indicators and relying on the descriptive analytical approach to the collected data, and to come up with realistic results about this phenomenon understudy. The results showed that all indicators used in research to determine the existence of tax evasion in Libya showed that its volume is very high and has negatively affected the contribution of tax revenues to pubic revenues, as it did not exceed 8.8%. It also led to a weakness in tax capacity, which did not exceed 3.9%. The study also showed that the weak efficiency of the tax and Customs Authority and the failure to implement deterrent penalties reduced the possibility of reducing this phenomenon the study recommended the necessity of applying penalties to tax evasion and activating laws, along with supporting and developing the tax administrative apparatus and raising tax awareness among citizens. The study also included another important set of results and recommendations. Keywords: Tax evasion - Income tax revenue - Customs duties - Public revenues.