This study investigates the impact of IFRS 15 adoption on corporate income tax in Iraqi contracting companies. It examines how changes in revenue recognition influence taxable income compared to the Iraqi unified accounting system. The analysis is based on financial data from a sample of private contracting firms over the period 2019–2022. A comparative approach is employed to evaluate differences in tax amounts under traditional accounting and IFRS 15, while a paired t-test is used to assess statistical significance. The findings indicate that the adoption of IFRS 15 leads to significant changes in revenue measurement and, consequently, corporate income tax liabilities. The results show an overall increase in total tax amounts under IFRS 15 amounting to 242,633,765, driven by differences in the timing and measurement of revenue recognition under the performance obligations model. The t-test confirms that these differences are statistically significant at the 5% level (p = 0.041). The study provides empirical evidence on the tax implications of IFRS 15 in an emerging economy and highlights the importance of aligning accounting standards with tax regulations to ensure consistency, transparency, and improved financial reporting quality.