A payment made to the writer of a compound option in the case that the call option is exercised in order to obtain a put option. Back fee is a premium charged at the second portion of the option, since a compound option is an option to purchase an option.
Compound options are most commonly used by mortgage originators as a way to mitigate risk. The back fee is offered at a premium, because it provides an investor with the ability to wait before executing an option.
Investment dictionary. Academic. 2012.