Razi University

  The significant dependence of Iraq's government budget on oil revenues and the limited share of tax revenues and other non-oil revenues are major challenges of this country's financial structure. This study was conducted to examine the relationship between tax revenues and both revenue diversification and the adequacy of Iraq's government budget over the period 2005-2024. To measure revenue diversification, the Herfindahl-Hirschman Index (HHI) and the Diversification Index (DIV) were used, and to assess budget revenue adequacy, the ratio of government revenues to government expenditures (EFF) was used. Tax revenues, oil revenues, economic growth, and inflation were also considered explanatory variables. According to the results of unit root and variable integration tests, the Autoregressive Distributed Lag (ARDL) model and the cointegration boundary test were used. The results showed that in the budget revenue adequacy model, there is a long-term relationship between the variables, and the error correction coefficient is -0.591, meaning that about 59 percent of short-term disequilibrium is adjusted in each period. In the long term, the impact of tax revenues on revenue adequacy was positive but statistically