If your long option expires even .01 in the money it will be automatically exercised, unless you file a contrary exercise notice. As others have said, your broker may liquidate your position if you don't have the capital to cover the exercise. If you are short an option, it is a bit different. A short out of the money option may be assigned or an in the money one may not be. This is because the owner of the option has time after the close of the stock to decide whether or not to exercise it. Their decision will based on after market trading in the stock. For example say I am long the MSFT 135 puts. MSFT closes at 136, so normally I wouldn't want to exercise them, as they are out of the money. But, say just after the close some news comes out and MSFT falls to 131 in after market trading. Now it would be advantageous to exercise these puts.
Generally the broker must notify the OCC by 530pm et. Different brokers will have different cutoff times for their customers in order to give themselves time to make this deadline. My broker's cutoff time is 5pm et, but will use "best efforts" after this time. Note that on half days, such as before the July 4th holiday, the cutoff time is earlier.
This means that from the perspective of a seller, they can confirm that their position is fully closed at max a day after the cut off is that correct ? After that the sold option is completely closed and it will not be exercised by the buyer is that correct ?