Step 2 of 4 · ProjectsTax engines
OpenTax Engine
Deterministic US federal and state tax engine for AI agents with proof trees for each result.
What it does
Give it plain facts (filing status, wages, children) and it returns US federal and state tax with a proof tree: every rule applied, the law behind it and each assumption. It is TypeScript, run from the command line, a browser file, an npm package or an MCP server. The README says it is not tax advice, that some rules approximate or refuse, and that closed-source use needs a commercial licence.
Where it fits on the map
Similar projects
Of the same kind, for a shared jurisdiction or tax area. Not a ranking.
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Maintain this project?
Link to this page from your README, so readers find the facts, the notes and where it fits. The badge is a small SVG served from this site.
[](https://tax-oss.com/projects/opentax-engine/)