August 30, 2026
Assignment isn't a decision your broker makes about you. It's a chain of steps with named parties, a fixed timeline, and one point where you stop having a choice.
The most common wrong mental model is that your broker looked at your account and decided to assign you. Assignment runs the other way, and it starts with someone you'll never know about.
The owner of the option decides to exercise. Their broker submits an exercise notice to the Options Clearing Corporation, which is the counterparty to every listed option in the United States. The OCC doesn't know who you are; it knows only that some number of contracts in that series have been exercised and an equal number of short positions have to absorb them. It assigns the exercises to clearing member firms at random, in proportion to their short open interest.
Your broker then allocates its share to individual accounts. Firms use either random selection or first-in-first-out, and they have to disclose which. Nothing about your account, your strategy, or your position size enters into it at any stage. It's a lottery run twice.
This is the part that surprises people, because assignment happens while you're asleep.
Exercise notices are submitted after the market closes. The OCC processes them overnight. Your broker allocates them and posts the result before the next session opens. You go to bed short a put and wake up owning 100 shares.
You cannot cancel an assignment once it's been made. There's no appeal and no window. The position is yours, and the earliest you can act on it is the next open, which means you carry the overnight gap whether you want it or not.
At expiration the timeline is longer and worse. An option that finishes in the money on Friday is exercised over the weekend, and the shares appear Monday morning. You've been long the stock since Friday's close but you couldn't trade it, and Monday can open anywhere.
Doesn't matter. The OCC automatically exercises expiring options that finish in the money by one cent or more, unless the owner files an instruction not to. Three cents past your strike is the same as three dollars past it as far as the machinery is concerned.
This is worth internalizing before your first expiration Friday, because the position that looks safe at 3:50pm is the one that produces a $5,000 stock purchase you weren't planning on. If you don't want the shares, close the contract during the session. Hoping it drifts back is not a plan.
The short option disappears. In its place, 100 shares appear and cash equal to strike times 100 leaves your balance. Most brokers show the cost basis as the strike, not the strike minus the premium you collected. The premium reduces your basis for tax purposes, but the platform usually won't do that arithmetic for you, which means the screen will make the position look slightly worse than it is.
If you sold the put cash-secured, the money was already set aside and nothing dramatic happens. If you sold it on margin against less than the full amount, this is where the loan appears, and if the account can't support the position you'll get a maintenance call or a liquidation, at your broker's discretion and on their schedule rather than yours.
Stock and most ETF options are American-style, so the owner can exercise any day before expiration. Almost nobody does, because exercising early throws away whatever time value is left in the contract, and selling the option is worth more than exercising it.
The exception is when there's essentially no time value left to throw away. A deeply in-the-money put with a week to go may be trading at close to its intrinsic value, at which point the owner loses nothing by exercising and gets their cash sooner. Deep in the money and close to expiration is the combination to watch.
For short calls, the trigger is dividends. An owner of a call that's in the money will sometimes exercise the day before the ex-dividend date, specifically to own the shares in time to collect it. If you're short calls on a dividend payer, the day before ex-dividend is the day assignment risk spikes.
It's worth saying plainly, because the language around it — getting assigned, being put the stock — makes it sound like something went wrong. If you sold a cash-secured put at a strike you'd genuinely buy at, assignment is the trade working as designed. You collected a premium to agree to buy, and now you're buying.
What's actually worth examining is whether the strike was one you'd have chosen on the day it arrived, at the price it arrived at, with whatever news came with it. That's a question about the original decision, and assignment is just the moment it becomes concrete.