Open-source tax engine hits 96% on TaxCalcBench with Claude Sonnet 5
Intelligent_Prompt18 · reddit · 2026-07-24
OpenTax MCP hits 96% on TaxCalcBench and beats prior leaders
This open-source tax engine scored 96% on TaxCalcBench, which the poster says is the highest score recorded so far, surpassing Fable 5 and Sol when paired with Claude Sonnet 5.
- The two misses were cases where the benchmark itself had inconsistencies, later acknowledged by the maintainers.
- The pitch is that the engine is deterministic, so AI models can use it for research and tax prep with fewer calculation mistakes.
- The project is exposed through OpenTax Invaro at a public MCP endpoint.
Related event: Open-Source Tax Engine Hits Record 96% on TaxCalcBench(4 posts)→
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