Hey Product Hunt! I'm the maker of Viva La Tax. I started this because I wanted to see the actual formula behind every number on my tax return. I also wanted to see how far we can push an AI harness with a deterministic core. The architecture is spec-driven: every IRS form line is documented in a YAML file with the formula, the IRS instruction reference, and the edge cases. Every spec entry has a unit test. The chain goes: IRS instruction → spec → test → engine code → your return. The whole thing is TypeScript with decimal math, Zod validation, and a Next.js frontend. It handles most individual tax situations: W-2 wages, self-employment, investments, rental income, crypto, retirement distributions, education credits, and more. Six states have deeply validated engines; the rest use a generic engine with published tax brackets. Self-hosting is `docker compose up`. Hosted version is at vivalatax.com. Would love your feedback, like on what tax situations to prioritize next!

Viva La Tax

Open-source tax engine — file for free, audit every number

Open-source tax engine — file for free, audit every number