Methodology changelog
Every engine change, on the record.
Our correction policyis simple: when a calculation issue is found, we fix the engine, add a regression test, and record it here — including the mistakes. A tax product that only publishes its wins isn't telling you anything.
Sample report Form 8938 verdict made engine-consistent
The published sample report hardcoded “Form 8938 required: Yes” next to figures below the printed thresholds, and its asset total wrongly included US-domiciled holdings. The sample case now carries explicit foreign bank accounts, every threshold verdict is derived from the same rule the engine applies, and a regression suite replays the sample through the real engine so the two can never disagree again. The package PDF now also names the exact test crossed (end-of-year vs any-time) and explains how the specified-foreign-assets figure is composed.
Affected: Sample PFIC report · package PDF Form 8938/FBAR section · Verified against: IRS Form 8938 instructions (reporting thresholds for taxpayers living abroad)
Form 8938 any-time test and foreign-only asset base
The FATCA threshold check previously ran the end-of-year test only and compared the total portfolio (including US-domiciled assets) against the threshold. It now runs both statutory tests — end-of-year and maximum-value-during-year — against specified foreign assets only, with foreign accounts contributing an explicit EOY balance when provided (never assumed equal to their maximum).
Affected: Form 8938 threshold check · triggered-forms detection · Verified against: IRS Form 8938 instructions; 26 CFR §1.6038D-2
FBAR computed from entered accounts
FBAR previously surfaced as an unconditional attestation request. The engine now aggregates the maximum annual balance across entered foreign financial accounts and computes the $10,000 verdict, while still requesting confirmation that no accounts are missing.
Affected: FBAR (FinCEN 114) check · Verified against: 31 CFR §1010.350; FinCEN Form 114 instructions
PFIC elections now drive the computation (no fabricated §1291 worst case)
The QEF / mark-to-market / §1291 election previously did not change the computed tax, and a fixed-shape §1291 “worst case” was estimated from assumptions (5-year hold, zero prior distributions). Elections now branch the math: MtM includes the §1296 gain in ordinary income; QEF requires the fund's Annual Information Statement and is otherwise reported as needs-input; §1291 charges are computed only from actual dispositions with known acquisition dates and basis — never fabricated.
Affected: Form 8621 computation · per-holding election chooser · package PDF · Verified against: IRC §§1291, 1295, 1296; IRS Form 8621 instructions (Rev. Dec 2025)
§1291 excess-distribution charge on actual dispositions
Dispositions of a known PFIC with explicit acquisition date and cost basis are now taxed under the §1291 excess-distribution regime: gain allocated ratably over the holding period, prior-year slices taxed at each year's top statutory rate with §6621 underpayment interest compounded per year. PFIC dispositions are excluded from the normal capital-gain pass so nothing is taxed twice.
Affected: Form 8621 Part V · Schedule 2 line 17p · Verified against: IRC §1291(a),(c); IRC §6621 quarterly rate tables
FEIE (§911) stacking and NIIT (§1411) added
Form 2555 exclusion computed with the §911(f) stacking worksheet (tax on income including the add-back minus tax on the exclusion alone), capped at the year's maximum. NIIT computed as 3.8% of the lesser of net investment income and MAGI over the filing-status threshold — flagged needs-input when MAGI is not supplied rather than approximated.
Affected: Form 2555 · Form 8960 · 1040 summary · Verified against: IRC §911(f); IRC §1411; Form 2555 instructions
Golden-test harness for tax math
Introduced hand-derived reference cases cross-checked against independent bracket calculators before being committed — federal brackets, LT capital-gain stacking, Form 1116 credit cap, FIFO realized gains, threshold arithmetic. Every engine change since must pass this suite.
Affected: Entire tax engine · Verified against: Rev. Proc. 2024-40 (2025 inflation adjustments)
Last reviewed . Known limitations are listed per form on the supported-forms page.