Running The Book Through Expiry

Expiry is the one day a derivatives position stops being an abstract mark on a screen and turns into an actual decision with a deadline. Every open option either expires worthless, gets automatically exercised, or has to be explicitly exercised or offset by the holder before a hard cutoff time — and a desk that lets that deadline arrive without a plan is letting the exchange's default rules decide the outcome instead of deciding for itself.

The first job on expiry day is simply knowing what's actually in the book: which options are in the money, by how much, and whether any of them sit close enough to the strike that a small final-hour price move could flip them from expiring worthless to being deep in the money, or vice versa — this is pin risk, and it's the single biggest source of expiry-day surprises. The second job is deciding, for anything in the money, whether to let it exercise automatically, exercise it manually, or close the position in the market before the cutoff; automatic exercise thresholds exist but they're a blunt default, not a substitute for a decision, especially for a large or unusual position. The third job is making sure whoever needs to know — margin, operations, clearing — actually knows what's coming, because an exercised option becomes a stock position overnight, with its own margin and settlement requirements that need to be ready for on Monday morning.

Worked example

A desk holds 500 short call contracts, strike $100, with the underlying closing at $100.15 on expiry day. That's barely in the money — a fifteen-cent move against the desk in the final minutes of trading could easily leave it either flat or fifty cents in the money by the close, and pin risk means the exact settlement price near a heavily-traded strike is genuinely hard to predict in the last hour. Rather than wait and find out, the desk decides in advance: if the underlying closes anywhere above $100.00, the position will be treated as in the money and hedged accordingly ahead of the close, so there's no overnight surprise about whether 50,000 shares of stock will show up in the account Monday morning needing to be sold.

The practical failure mode is doing nothing and letting exchange default rules and standing instructions handle it. Automatic exercise cutoffs vary by product and can differ from what a trader assumes, and a position left unmanaged into the close can convert into a stock position of a size or direction nobody planned for, discovered only when the next day's positions report doesn't match expectations.