Does the Put-Call Parity Relationship Hold True for American-Style Options?

The put-call parity relationship holds only as an inequality for American-style options. Because American options have the right to early exercise, the relationship is expressed as an upper and lower bound.

Specifically, the value of the American call plus the present value of the strike price is generally greater than or equal to the value of the American put plus the underlying asset price. The potential for early exercise prevents the strict equality seen in European options.