Hello! I've googled and searched the forum but a few specifics are still unclear to me as to how assignment of puts I've sold happens (and when). Let's assume I've sold some puts on the SPY at strike 150, and on a Friday close the SPY is trading at 149. To my understanding: The puts can be exercised by the buyer any time after the markets close on Friday (16:00) until Saturday if the price is below the put strike (in my example 150). If at the Friday close (regular trading hours) SPY is 149, and then the after hours price of the SPY goes above 150 (strike), and the put buyer has still not exercised his put, he may not (at that point) exercise it, and I will not get assigned. At Interactive Brokers I will know immediately if I am assigned, when I am assigned. This will show up as a long position in the SPY and the negative unrealized PnL will be equal to the price difference (price - strike) * option contract count * 100. Assignment of ITM Puts happens 99.9% of the time after expiry. Are any of these points incorrect? On one website it seemed that they said the brokers will automatically assign the puts based on only (and nothing but) the very last Friday after-hours traded price of the SPY (on any exchange). Could this be true also, so I don't have to worry about anything except the very last print? Understanding assignments is an important part of spreads, if something unexpected happens and knowing this in more detail would certainly help me understand the risks a little better.