Early Assignment Risk in Systematic Overwriting

A systematic overwriting program sells call options against a stock holding on a rolling schedule — for example, writing one-month calls every month against a long equity book to collect premium. American-style equity options can be exercised by the holder at any time before expiration, not only on the expiration date, so the short calls in an overwriting program can be assigned early, forcing the shares to be delivered before the desk had planned to sell them.

Early assignment happens almost exclusively around dividends: if a call is deep in-the-money and the dividend the holder would capture by exercising and holding the stock exceeds the remaining time value in the option, exercising early can be rational for the option holder. A systematic overwriting book that ignores this can find its shares called away right before an ex-dividend date, missing the dividend it was expecting to earn and needing to re-establish the position — often at a worse price, plus transaction costs it hadn't budgeted for.

A simple check the desk runs before each ex-dividend date: for every short call trading deep in-the-money with little time value left, compare the dividend to the option's remaining extrinsic value; if the dividend is larger, assume assignment is likely and plan the roll or re-purchase in advance rather than reacting after the fact.