Governments worldwide cannot collect the required tax revenue for their planned activities. This study aims to assess how inefficient VAT audit function and related factors affect tax revenue performance in Amhara Region, Ethiopia. The study used primary data sources from 377 VAT registered taxpayers in Amhara Region. It also used the Ability to Pay theory of taxation, structural equation model, path diagram, and multiple regression with SPSS/AMOS software for data analysis to identify the relationship between VAT audit and tax revenue performance. Even though the Amhara Region has revenue potential to cover its expenditures, because of inefficient VAT audit functions, poor system of tax education, lack of tax resources, and long time served tax rate, the tax revenue performance is inefficient. The study assured that VAT audit and tax education significantly affect tax revenue performance. The scarcity of resources for the VAT audit function is a critical problem. Even if the existed technology networked up to woreda levels, tax auditors did not use this system appropriately. Long-time-served tax rates also greatly influence tax revenue performance. The study recommended that there should be a chain mentor relationship between experienced auditors to new and ineffective auditors. The government should supply appropriate technology that is simple to use and quickly detect tax evasion. The existed tax rate and the system of tax education should be revised. The above findings are essential for taxpayers, policymakers, and tax authorities to understand, analyze, and use the main causes of VAT audit problems on tax revenue performance.