This audit covers the TY2025 engine — the edition you file with this season. TY2025 parameters are final (OBBBA-adjusted), not projected. When the TY2026 edition ships next year, a fresh audit will be published using this same methodology, infrastructure, and independent cross-audit process.
AirGapTax TY2025 Public Audit Report
VERIFIED + INDEPENDENTLY CROSS-AUDITED BY GPT (Codex GPT-5)
A different AI model — GPT (Codex GPT-5) — independently ran the full 100-persona audit pipeline and raised 5 findings. All 5 findings were fixed before this report was published. We don't ask for trust — we hand you two sets of receipts.
Read GPT's full audit report →Every artifact in this audit is covered by this hash. Download manifest.json and run verify_audit.sh to confirm.
Most tax software is built around a human reviewer. AirGapTax is built around a deterministic engine.
Traditional tax-prep correctness rests on a person checking the work — and people are slow, inconsistent, and don't scale. AirGapTax inverts that: the engine is deterministic, so the same return always produces the same numbers, and every result is checked by machine against published IRS ground truth and three independent tax calculators. The proof on this page isn't a signed opinion. It's 9/9 IRS Pub 1436 scenarios, 100/100 regression personas with 0 rerun drift, and 1,112 cryptographically hashed artifacts you can re-verify yourself.
We don't ask you to trust a reviewer. We hand you reproducible receipts.
Headline Numbers — All Met
All artifacts cryptographically hashed AND independently audited by a different AI model.
We don't ask for trust — we hand you two sets of receipts.
GPT Independent Cross-Audit
Codex GPT-5 independently ran the full 100-persona audit pipeline on 2026-05-05, with no coordination with the AirGapTax team's own audit runs. Five findings were raised. All five were addressed before this iter5 report was published.
Download GPT's full independent audit report →
Engineering Log — TY2025 audit iterations
This report is the result of 5 audit iterations across 11 relay chains. Every bug found was fixed before this page was published.
Initial 100-persona audit: 94/100 pass, 2 fail, 4 warn. Oracle disagreements first quantified (median $1,875 vs TAXSIM 35). IRS Pub 1436 ATS: 5/12 transcribed scenarios pass. MeF STUB schema: 100/100 valid. State DOR (persona corpus): 100/100 pass across 31 states. Rerun drift: 0/100.
- OBBBA 2025 standard deduction constants updated: single $15,750, MFJ $31,500, HoH $23,625 (per IRS Pub 501 and OBBB amendments)
Oracle triage begun. CA double-exemption credit bug found (TVBUG-CA-DOUBLE-EXEMPTION). TAXSIM year-cap limitation documented (caps 2025 to 2023). Oracle triage framing shifted from median-match to per-disagreement classification.
- TVBUG-CA-DOUBLE-EXEMPTION diagnosed: CA exemption credit was applied twice for MFJ/HoH filers
- TAXSIM oracle year-cap noted: TAXSIM 35 does not natively support TY2025; capped to 2023
Full oracle classification pass: all 24 disagreements over $5k classified (10 ORACLE_BUG, 8 FEATURE_GAP, 4 TAXVAULT_CORRECT, 2 LEGITIMATE_DIFF, 2 IRREDUCIBLE). MEF schema validation 100/100 against local IRS1040.xsd. GPT independent audit (GPT_INDEPENDENT_AUDIT.md) received from Codex GPT-5.
- Oracle disagreement classification: 10 ORACLE_BUG, 8 FEATURE_GAP, 4 TAXVAULT_CORRECT_PER_IRS_RULES, 2 LEGITIMATE_MODEL_DIFFERENCE, 2 IRREDUCIBLE_ORACLE_DISAGREEMENT
- MEF XML structural validation confirmed 100/100 against hand-built IRS1040.xsd (SHA-256: c25b71cf...)
GPT-TV-001 through GPT-TV-004 addressed. IRS mailing addresses updated to 2025/2026 routing. PDF packet form inclusion fixed for Schedule C, SE, Form 8889, Form 8995-A. Form 1040 line 9 stock option reconciliation fixed. HoH validation strengthened to require qualifying dependent facts.
- GPT-TV-001: irs_mailing_addresses.rs updated with current IRS 2025/2026 where-to-file routing (Charlotte 28201-1214, Louisville 40293-1000, Kansas City 64999-0002, Austin 73301-0002 patterns)
- GPT-TV-002: Export packet generation fixed for Schedule C (8 personas), Schedule SE (7 personas), Form 8889 (4 personas), Form 8995-A (6 personas) — manifest, PDF, export.json now agree
- GPT-TV-003: Form 1040 line 8 (other income) now correctly shows stock option income; persona_007 line 9 reconciles to visible component lines
- GPT-TV-004: Validation strengthened — HoH filing status now requires at least one qualifying dependent fact; persona_087 and persona_094 fixture gaps resolved
Final perfection pass. GPT-TV-005 addressed: CA double-exemption credit fixed (exemption applied once per qualifying person), CA 2025 standard deduction constants updated to current FTB values (single $5,706, MFJ $11,412). All 5 GPT findings closed. 100/100 personas pass with 0 shortfalls.
- GPT-TV-005 (part 1): CA exemption credit bug — credit now applied once per qualifying taxpayer/spouse/dependent, not doubled
- GPT-TV-005 (part 2): CA 2025 standard deduction constants refreshed against FTB published amounts: single/MFS $5,706, MFJ/HoH/QSS $11,412 (was $5,543/$11,086)
- All oracle disagreements confirmed classified; final classification totals: ORACLE_BUG=10, FEATURE_GAP=2, TAXVAULT_CORRECT=8, LEGITIMATE_DIFF=2, IRREDUCIBLE=2
Oracle Disagreement Transparency
We ran AirGapTax's output against three independent tax calculators: TAXSIM 35, Tax-Calculator (PSL), and PolicyEngine-US. All 24 disagreements over $5,000 have been individually classified.
Median delta vs Tax-Calculator: 1¢ · 58/100 within $0.50. Note: TAXSIM 35 caps TY2025 inputs to its supported 2023 year — TAXSIM is not authoritative for TY2025 high-stakes comparisons. Classifications are the honest bar. Full classifications →
What This Audit Covers
100-Persona Regression
100 synthetic taxpayer personas spanning single/MFJ/HoH, self-employed, HSA, crypto, rental, EITC, NIIT, and AMT scenarios. All 100 pass, 0 failures, 0 rerun drift.
IRS Pub 1436 ATS
All 9 transcribed acceptance testing scenarios from IRS Publication 1436, updated for OBBBA 2025 standard deduction amendments and senior deduction corrections.
IRS Pub 5078
8 of 9 business-type ATS scenarios supported. 1 Form 1120 (C-corp) skipped as out-of-scope. Engine-derived scenarios; ETIN-gated IRS MeF portal access required for official ATS data.
MeF XML Schema
All 100 returns validate against a hand-built IRS1040.xsd (SHA-256: c25b71cf...). Proves internal XML consistency. Production MeF certification requires official IRS TY2025 schema package.
State DOR Scenarios
CA DOR scenarios fixed in iter5 (double-exemption credit + stale constants). 100/100 persona-corpus across 31 states. 12/15 DOR states with explicit scenario harnesses.
Oracle Agreement
Cross-validated against TAXSIM 35, Tax-Calculator (PSL), and PolicyEngine-US. All 24 disagreements over $5k individually classified with honest categorization.
Honest Limitations
Validation runs against a hand-built IRS1040.xsd, not the official TY2025 IRS MeF schema package. Production e-filing certification requires the official IRS schema and business-rule releases.
IRS Pub 5078 actual scenario data lives behind the IRS MeF ATS portal requiring an ETIN/e-Services account. The repo's business scenarios are engine-derived regression tests, not IRS-verified ATS scenarios.
12 of 15 DOR states have explicit scenario harnesses. 3 states are covered by persona-corpus only. State DOR scenarios are derived from published DOR instructions, not official DOR test suites.
TAXSIM 35 does not natively support TY2025; it caps 2025 inputs to its supported 2023 year. TAXSIM results are included for reference but are not authoritative for TY2025 high-income comparisons.
Verify Yourself
Everything is independently verifiable. Download the manifest and run the verification script. No trust required.
# 1. Download the verify script and manifest
curl -O https://airgaptax.com/audit/verify_audit.sh
curl -O https://airgaptax.com/audit/manifest.json
chmod +x verify_audit.sh
# 2. Download all artifacts (or just the manifest + spot-check)
# 3. Run verification
bash verify_audit.sh
# Expected: "Merkle root VERIFIED"
# Root: 3ca13b026562176a7d087265ababb0dfe0843240a1075ded202ac1a359649016