Book excerpt: Despite the criticality of tax administration (TA) reforms in enhancing domestic revenue mobilization, few studies have attempted to quantify the revenue impact of such reforms. This paper fills this gap by estimating the revenue yields associated with various tax administration capabilities, based on the International Survey on Tax Administration (ISORA), the Tax Administration Diagnostic Assessment Tool (TADAT), and TA reform episodes datasets (identified by Akitoby et al., 2020). It uses a Hausman-Taylor cross-country panel regression and an event study for specific TA reform episodes. Our results (using the ISORA data) show that an increase in the overall strength of TA from the 40th percentile to the 60th percentile is associated with an increase in tax revenue by 1.8 pp. of GDP (with a 95 percent confidence range of 0.5‒2.6 pp. of GDP). Similarly, the event-study assessment shows that sustained TA reforms led to an increase in tax revenues between 2 to 3 pp. of GDP, in line with the experience in three country cases (Jamaica, Rwanda, and Senegal). Also, the revenue yields are increasing over time to more than 3 pp. of GDP after the 6th year following a comprehensive reform. The analysis also highlights the significant impact of specific measures including: i) strengthening compliance risks management, ii) enhancing public accountability, iii) establishing Large Taxpayer Offices (LTO), iv) strengthening accountability and transparency, and v) enhancing timely filing of tax declarations.