Put options are bets that the price of the underlying asset is going to fall. Puts are excellent trading instruments when you’re trying to guard against losses in stocks, futures contracts, or commodities that you already own. When you buy and sell puts, it pays to know the difference between a naked or covered put option.

Buying naked and covered put options

Buying a put option without owning the stock is called buying a naked put. Naked puts give you the potential for profit if the underlying stock falls. But if you own a stock and buy a put option on the same stock (a covered put), you’re protecting your position and limiting your downside risk for the life of the put option.

A good time to buy a put on a stock that you own is when you’ve made a significant gain, but you’re not sure you want to cash out. You can also use puts to protect against short-term volatility in long-term holdings.

In the first instance, your put option acts as an insurance policy to protect your gains. In the second instance, if your put goes up in value, you can sell it and decrease the paper losses on your stock. You decide which put option to buy by calculating how much profit potential you’re willing to lose if the stock goes up.

Selling naked and covered put options

Selling naked put options is similar to buying a call option, because you make money when the underlying stock goes up in price. Selling naked puts means you’re selling a put option without being short the stock, and in the process, you’re hoping that the stock goes nowhere or rises, which enables you to keep the premium without being assigned.

If the stock falls in a big way, and you get assigned, you can face big losses from having to buy the stock in the open market to sell it to the party exercising the put you sold.

You need to put up collateral to write naked puts, usually in an amount that is equal to 20 percent of the current stock price plus the put premium minus any out-of-the-money amount.

Here is how it works: ABC is selling at $40 per share, and a four-month put with a striking price of $40 is selling for 4 points. You have the potential to make $400 here or the potential for a huge loss if the stock falls. Your loss is limited only because the stock can’t go below zero.

The amount of collateral you’d need to put up would be $400, plus 20 percent of the price of the stock, or $800. The minimum you’d have to put up, though, would be 10 percent of the strike price plus the put premium, even if the amount is smaller than what you just calculated.