Free, private, open-source tax prep. Private, browser-based tax preparation powered by an open-source tax engine.

TelosTax is a free, open-source tax preparation app for the 2025 tax year, built entirely with AI. Your tax data never leaves your browser — all calculations happen client-side using the @telostax/engine library, encrypted at rest with AES-256-GCM.

• TelosTax @ GitHub.

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Make sure your equity generates wealth, not a shocking tax bill. Stock options, RSUs, job offers, and taxes—a detailed reference, including hundreds of resources, explained from the ground up, for employees and managers.

• The Open Guide to Equity Compensation @ GitHub.

Open models to compute tax and benefit systems. OpenFisca is a versatile microsimulation free software. The most widely adopted free and open-source engine to write rules as code.

Government departments, lawmakers and civil society finally share a common language to debate and activate social and fiscal policies: OpenFisca enables collaboratively modelling laws and regulations and making them computable over open APIs for developers, datascientists and researchers.

• OpenFisca @ GitHub.