Covered call writing is either the simultaneous purchase of stock and the sale of a call option, or the sale of a call option covered by underlying shares currently held by an investor. Generally, one call option is written for every 100 shares of stock owned. The writer receives cash for selling the call but will be obligated to sell the stock at the call's strike price if assigned, thereby capping further upside stock price participation. In other words, an investor is "paid" for agreeing to sell his holdings at a certain level (the strike price). For this reason the covered call is considered a neutral to moderately bullish strategy. On the downside, limited stock price protection is provided by the premium received from the call's sale.
The upside profit potential if assigned is limited to the premium received from the call's sale plus the difference between its strike price and the stock purchase price. If assignment is not received and the call expires out-of-the-money and with no value, the upside profit potential is any gain in share value plus the premium received. The downside loss potential is substantial and comes entirely from owning the underlying shares and is limited only by the stock declining to zero. The break-even point is an underlying stock price equal to the purchase price of the underlying shares less the premium received. As with any short option position an increase in volatility has a negative financial effect on the covered call while decreasing volatility has a positive effect. Time decay has a positive effect.