FA-62535 / Tax bracket computation / Member archive

The exemption phase-out is computed on total AMTI instead of the excess · case 05

The exemption disappears for filers barely over the threshold.

Member previewVariant 5 · 3 implementations · 6 checks per implementation

Case contract

solve(amti, regular_cents, status): stipulated AMT, whole dollars. Exemption: single 85700 (phase-out threshold 609350), mfj 133300 (threshold 1218700). The exemption is reduced by 25% of AMTI above the threshold, with the reduction rounded down to whole dollars, never below 0. Base = max(0, amti - exemption). Tentative minimum tax = 26% of base up to 232600 plus 28% of base above 232600 (in cents: dollars times percent). AMT = max(0, TMT - regular tax). Return [exemption, tmt_cents, amt_cents].

Why this case matters

Tax computations hinge on which slice, threshold, ordering and rounding rule applies at each step; a misplaced boundary silently misstates liabilities.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
regression phaseout-base 1	`[0, 19982500, 17482500]`	`[55469, 18429368, 15929368]`	Failed

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