A strong answer. “The instinct I'd want to establish first is that a break is never nothing. Two hundred shares is small enough that it's tempting to write it off, and small breaks are frequently the visible edge of a systematic error that is also affecting positions you haven't noticed.

Method, cheapest first. Is it a timing difference or a real difference? A trade booked on our side today and settling tomorrow will show as a break against a settled-basis custodian statement and is not an error at all. That single check resolves a large share of breaks in a minute.

Then: does the quantity mean anything? Two hundred shares against a corporate action ratio is suspicious — a bonus or split we processed and the custodian did not, or applied on a different date. If the security had an ex-date recently, that is where I'd look next, because corporate actions are the most common source of real breaks and the most likely to be systematic.

Then trade-level matching: pull our fills and their movements and match on time, price and quantity. What's left is usually one trade, and then it's a question of who booked it wrong — and whether it was booked to the wrong account, which is a different and more serious problem.

What I'd do in parallel, and this is the part that distinguishes the answer: quantify the exposure now. Two hundred shares of an illiquid stock in a volatile market is a real market risk sitting unhedged while we investigate, and someone should know about it immediately rather than at the end of the investigation. Operations that only reports resolved breaks reports too late.

And if it doesn't resolve today, it gets aged, owned by a named person, and escalated on a schedule. Every serious operational loss I've read about was preceded by breaks that were carried for weeks because nobody owned them.

Then the systemic question: is this the first one, or the third this month on the same security or the same counterparty? If it's a pattern, fixing this instance is the least valuable thing I could do.”