Every OpenTax computation traces to an authoritative IRS publication. Our rules engine is deterministic, open-source, and tested against real-world tax scenarios.
Every computation node mapped to its authoritative IRS source — Rev. Proc. 2024-40, Pub 501, IRC sections, and form instructions.
View sources10 real-world scenarios with specific inputs, expected outputs, and computed results. Each scenario shows the exact dollar amounts and pass/fail status.
View scenariosHonest disclosure of what OpenTax does and does not cover for Tax Year 2025. We believe transparency builds trust.
View limitationsA deterministic rules engine with full traceability, tested against IRS publications and real-world returns.
Pure functions with no randomness. Same inputs always produce the same outputs.
Every computed number carries its source document, IRS citation, and confidence score.
All monetary values stored as cents. No floating-point rounding errors.
900+ unit tests and end-to-end integration scenarios validate every computation path.
OpenTax is open-source. Review every line of our rules engine, run the test suite, or file a tax-accuracy issue.