FA-62508 / Tax bracket computation / Member archive

The first bracket rate is reported while deduction headroom remains · case 03

A filer earning below the deduction is told the next dollar is taxed at 10%.

Member previewVariant 3 · 3 implementations · 7 checks per implementation

Case contract

solve(gross, deduction, brackets): taxable = max(0, gross - deduction); tax uses the progressive slices. The marginal rate is the rate of the bracket containing taxable income with (lower, upper] semantics (income exactly at a threshold is in the lower bracket), and is '0' when gross < deduction (unused deduction absorbs the next dollar; at gross == deduction the next dollar is taxed at the first rate). The effective rate is tax / gross in basis points rounded half-up (0 when gross <= 0). Return [marginal_rate_string, effective_bps].

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 unused-deduction-marginal 1	`["10", 0]`	`["0", 0]`	Failed

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