The Urban-Brookings microsimulation tax model is a powerful tool for federal tax policy analysis. The model calculates tax liability for a representative sample of households, both under the rules that currently exist (current law) and under alternative scenarios. Based on these calculations, the model produces estimates of the revenue consequences of different tax policy choices, as well as their effects on the distribution of tax liabilities and marginal effective tax rates (which affect incentives to work, save, and shelter income from tax). The model is also a useful input to research on the effects of taxation on economic behavior. This paper describes the tax model's data sources and details its underlying statistical techniques. We also explain the capabilities of the tax model's individual income tax calculator and describe how the model estimates and distributes corporate, payroll, and estate taxes.