Revenue − expense → net result, for one fiscal year.

Window — same rules as the trial balance: fiscal_year defaults to the latest posted year, period_id narrows to one period of it, unknown values are 404 and a contradictory pair 422. A P&L is a flow statement, so no reading makes the sum of every fiscal year a company's result — hence no all-years mode (ZET-155). Opening batches post only to balance-sheet accounts, so they never enter this figure.

The cut — by the line's stamped fiscal_year_id FK, not by posting date; the response's fiscal_year_cut says so (see the trial balance; null only for a company that has posted nothing, ZET-166). For the full statement — per-account sections, the year's own account names, the problems list and the cash flow — use GET /companies/{id}/financial-statements, which cuts by a posting-date window instead, so the two can disagree for a short/long or shifted fiscal year; this route returns the three totals.