The holder of an American-style option can exercise his right to buy (in the case of a call) or to sell (in the case of a put) the underlying shares of stock.
They first must direct their brokerage firm to submit an exercise notice to OCC. For an option holder to ensure that they exercise the option on that particular day, the holder must notify his brokerage firm before that day’s cut-off time for accepting exercise instructions.
The brokerage firm notifies OCC that an option holder wishes to exercise an option. OCC then randomly assigns the exercise notice to a clearing member. For an investor, this is generally his brokerage firm chosen at random from a total pool of such firms. The firm must then assign one of its customers who has written (and not covered) that particular option.
Assignment to a customer is either random or on a first-in-first-out basis. This depends on the firm’s method. Ask your brokerage firm which method it uses for assignments.
The holder of an American-style option contract can exercise the option at any time before expiration. Therefore, an option writer may be assigned an exercise notice on a short option position at any time before expiration. If an option writer is short an option that expires in-the-money, they should expect assignment on that contract, though assignment is not guaranteed as some long in-the-money option holders may elect not to exercise in-the-money options. In fact, some option writers are assigned on short contracts when they expire exactly at-the-money or even out-of-the money. This occurrence is usually not predictable.
To avoid assignment on a written option contract on a given day, the position must be closed out before that day's market close. Once assignment is received, an investor has no alternative but to fulfill assignment obligations per the terms of the contract.
There is generally no exercise or assignment activity on options that expire out-of-the-money. Owners usually let them expire with no value. Although this is not always the case as post-market underlying moves may lead to out-of-the-money options being exercised and in-the-money options not being exercised.
What's the Net?
When an investor exercises a call option, the net price paid for the underlying stock on a per share basis is the sum of the call's strike price plus the premium paid for the call. Likewise, when an investor who has written a call contract is assigned an exercise notice on that call, the net price received on per share basis is the sum of the call's strike price plus the premium received from the call's initial sale.
When an investor exercises a put option, the net price received for the underlying stock on per share basis is the sum of the put's strike price less the premium paid for the put. Likewise, when an investor who has written a put contract is assigned an exercise notice on that put, the net price paid for the underlying stock on per share basis is the sum of the put's strike price less the premium received from the put's initial sale.
For call contracts, owners might exercise early to own the underlying stock to receive a dividend. Check with your brokerage firm on the advisability of early call exercise.
It is extremely important to realize that assignment of exercise notices can occur early, days or weeks in advance of expiration day. Investors should expect this as expiration nears with a call considerably in-the-money and a sizeable dividend payment approaching. Call writers should be aware of dividend dates and the possibility of early assignment.
When puts become deep in-the-money, most professional option traders exercise before expiration. Therefore, investors with short positions in deep in-the-money puts should be prepared for the possibility of early assignment on these contracts.
Volatility is the tendency of the underlying security's market price to fluctuate up or down. It reflects a price change's magnitude. It does not imply a bias toward price movement in one direction or the other. It is a major factor in determining an option's premium.
The higher the volatility of the underlying stock, the higher the premium. This is because there is a greater possibility that the option will move in-the-money. Generally, as the volatility of an underlying stock increases, the premiums of both calls and puts overlying that stock increase and vice versa.