FA-59528 / Subscription proration billing / Member archive

Sales tax on proration credit and debit lines: credit line tax reversal · case 03

Downgrade invoices over-collect tax because unused-time credits carry no tax reversal.

Member previewVariant 3 · 3 implementations · 8 checks per implementation

Case contract

Input {lines: [[signed cents, taxable]], rate_bp}. Tax is computed per taxable line, including negative credit lines (negative tax), each rounded half away from zero, then summed. Subtotal is the sum of all lines. Return [subtotal, tax, subtotal + tax].

Why this case matters

Credit lines on a prorated invoice must reverse the tax charged on the original period.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
regression 0	`[-31956, 172, -31784]`	`[-31956, -6, -31962]`	Failed

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