Pin risk occurs when the underlier of an option contract settles close to the option's strike value at expiration. In this situation, the underlier is said to have pinned. The risk to the writer (seller) of the option is that they cannot predict with 100% accuracy whether the option will be exercised or not. Therefore, the writer may end up with a residual position in the underlier. There is a chance that the price of the underlier may gap adversely, resulting in an unanticipated loss to the writer. In other words, an option position may result a large, undesired risky position in the underlier on the Monday following expiration regardless of the actions of the trader.
IMO, the risk is not only at the RTH closing time on expiration day. Option holder can exercise an option as late as 16:30 EST, 30 minutes after the RTH closing. When there is any price jump during the 30 minutes after RTH, it may put the option writer at risk.
Let's say you short 1 GOOG call 470 expiring, it closes at 468 at 16:00 EST on expiring Friday and GOOG jumps to 485 at 16:20 EST. Will you worry the assignment?
How do you handle the situation like this? Will always close the short position with extra cost a wise idea?
I don't write naked option but face the same problem with option spread.
TIA
/Daniel