Potential Risks of Box Spreads

Due to the nature and pricing of box spreads (and similar strategies), they can be especially susceptible to the risks associated with an early assignment. The following links explain what a box spread is and why a short option would be assigned early. 

All of these potential reasons for early assignment get priced into the options. Because of this, it can be possible to sell a box spread (or similar risk-free strategies) for more than the width of the spread. This gives the illusion of risk-free profits, but early assignment and the associated costs could wind up costing much more than the additional credit received.