The Health Insurance Reform Simulation Model (HIRSM) is designed to simulate the coverage, cost, and tax implications of health insurance coverage expansion proposals and other reforms to the health insurance system. The model uses nationally representative data on employers, workers, and those outside of the labor market. HIRSM simulates the behavioral choices of insurers, employers, and individuals under the current system and under reform, allowing us to predict the coverage consequences of various policies. It can simulate the effects of reforms affecting private insurance markets and public programs. This report details the model in its entirety and presents prototypical results.