Video Summary (1 and a half minutes)
The closing price of the stock on expiry establishes which options finish in the money and subject to exercise or assignment or those that finish out of the money, and worthless. Because option spreads involve both buying and selling of options, if the entire spread finishes out of the money, it either expires worthless, with nothing exercised or assigned. If a spread finishes completely in the money, it expires at its max value, with the options exercised and assigned, canceling each other out, and profits or losses determined. However, if only part of a spread is in the money, the position runs the risk of being assigned or auto-exercised and a resulting stock position may occur. Therefore many investors close spreads before expiry, if only part of the spread is in the money, or if the stock is close enough to the spread that that may occur.