FA-61663 / Options payoff and settlement / Member archive

FIFO realized P&L for option trades: closing a short lot books the price change with the long sign · case 03

Buying back a short option at a lower premium records a loss.

Member previewVariant 3 · 3 implementations · 8 checks per implementation

Case contract

Inputs trades [side B/S, contracts, premium], multiplier and fee per contract. Positions may be long or short. Each trade first closes opposite-direction lots oldest first; realized P&L per matched contract is (close - open) for long lots and (open - close) for short lots, times the multiplier. Any remainder opens a new lot in the trade direction. Fees = contracts traded * fee. Work in cents; return [net position, realized, fees].

Why this case matters

Option expiry, exercise and settlement engines move cash and shares; a wrong branch misstates obligations.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
regression short lot pnl sign 1	`[3, -1660.0, 17.0]`	`[3, -770.0, 17.0]`	Failed

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