Key PointsTax-Cruncher is a new open-source project for analyzing how tax policy affects taxpayer finances and incentives. Tax-Cruncher allows policymakers, researchers, and everyday taxpayers to analyze how changes to current tax law would affect a taxpayer’s financial situation. IntroductionTax-Cruncher is open-source software for users to estimate how policy reforms or alternative income scenarios could influence a taxpayer’s tax liabilities and incentives. The source code for Tax-Cruncher3 and the other modeling projects Tax-Cruncher depends on4 are open source and hosted on GitHub, and Tax-Cruncher is cross-compatible with other projects in the Policy Simulation Library.5 Users are encouraged to contribute to the project and welcome to modify the source code to fit their needs. Important taxpayer information relevant to some returns is not considered by Tax-Cruncher.