Tax math that
proves itself
Language models argue. Statutes don't. OpenTax is a computation oracle where every line of a return traces to the law that produced it — and every answer ships with a proof you can re-verify offline.
> compute_return { filing, income, documents: { w2s, f1099rs, dependents } }
{
"lines": {
"11_agi": "$162,100.00",
"16_tax": "$27,068.00",
"24_total_tax": "$27,373.00",
"34_refund": "$2,627.00"
},
"assumptions": [ ...every default, named and cited... ],
"corpusMerkleRoot": "sha256:6acf8e21a405c18d…"
}the hash pins the exact rule set — anyone can replay the proof
Cited, verbatim
Every rule in the corpus carries its statute — 26 U.S.C. section, effective window, and a verbatim source excerpt. No number enters the engine on model recall.
Provable
Every computation returns a Merkle-rooted proof: the facts, the rules, the arithmetic. Re-verify any answer offline, byte for byte.
Documents in, facts out
A deterministic compiler turns W-2 and 1099 boxes plus birth dates into engine facts — ages, dependent classifications, penalties, excess withholding — with zero judgment calls.
Refuses loudly
Anything outside the corpus refuses with a named reason instead of guessing. A wrong answer that looks right is the one failure mode we do not ship.
Federal + state
The complete scored federal Form 1040 line set in one call, plus a growing state layer — CA, IL, NY, VA — with the same citation discipline.
Differentially tested
Hundreds of hand-computed golden fixtures and a differential harness against PolicyEngine. When two engines disagree, one of us reads the statute again.
Give your agent an oracle
One MCP server. Grouped facts in, the full scored line set out — cited, rounded the way the forms round, and provable.
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