A call option on a put option. It gives the holder the right, without the obligation, to purchase a put option for a specified premium. This option belongs to the class of compound options or split-fee options in which the payoff of the second option involves the value of the first. Such options have two expiration dates and two exercise prices. Investors willing to establish positions with higher leverage levels than those tenable through regular options may use options on options.

The CoP option is also known as a caput.