The question in the subject is not related to when I, as a retail customer, can exercise options, but how long market markets/exchange members etc. can wait before deciding to exercise options. Lets say I have some options that is slightly in the money as trading stop on expiring day. I expect these options to be exercise and on that ground I might have been taking other positions (e.g. covering with a position in the underlying). My question is if I have a risk of news coming out after trading stop, that will cause the counterparty not to exercise? Or did he have to decide before trading stop (even if he is a market markets/exchange members etc.)