People on their way out have the least reason to sugarcoat and the most complete view of what working with you is like. An exit interview converts that into usable signal — if it is structured, safe, and actually read.
What to ask: the primary reason for leaving (one honest answer beats five polite ones), what worked and what didn't, whether they would recommend the company, whether they would return. Who should ask: someone other than the direct manager — feedback about a manager, softened to their face, is the most common loss. When: inside the notice period, but after the handover pressure eases and there is nothing left to negotiate.
The discipline that makes it worth the hour: treat one exit as an anecdote and five as data. Aggregate reasons across departures and read them next to the attrition trend — a single "compensation" is a negotiation that ended; three in two quarters is a market signal about your salary bands.
And the trust rule: the departing person should know who will see the raw notes.
In Helia, exit interviews are part of offboarding — the default checklist schedules and conducts one — and the record captures the primary reason, satisfaction and would-recommend scores, a would-return answer and what-worked / what-didn't notes, with an explicit flag controlling manager visibility; offboarding reasons then feed the dashboard's 12-month turnover breakdown.