The research investigates horizontal equity i.e., extent to which persons with similar income are treated equally, of personal income tax liabilities of nine (9) federal government MDA’s and institutions employees on the Consolidated and Unified Salaries Structure scheme in terms of; the minimum and progressive tax liabilities. Secondary data which includes the grade level, steps, statutory deduction and allowance, emolument is collected from the National Salaries, Income and Wages Commission (NSIWC) and FIRS. The data is analysed using multi-level linear modelling techniques i.e., MLM (due to the hierarchical nature of the data, large variance and within MDA’s sample dependency) to extract the residuals inputs used to compute the coefficient of residual variation ratio (CRVR). Dis-aggregating the data into minimum or progressive tax rate payments, it was founds that: employee charge on the minimum tax rate of 1% are generally horizontally equal, but the rate varied at lower- or upper-income class employee appear more horizontally equal relative to middle-income class employee, employee charged on the progressive tax rate of 7%-33% are however less horizontally equal relative to those with minimum tax rate with the lower and upper income class performing better than those at the middle income class. Overall, the lower- and middle-income earners are found to be less treated equally relative to a specific income group at the upper echelon where a lower horizontal inequality is found.
