Here is some information from "Ordering FAQ's" on the Customer Service page:
<h4>When will my order be processed if I pay by check?</h4>
Your order cannot be processed until we receive payment. Please be sure to promptly mail your check with the order number written on the check. If your check is not received within 10 days, your order will automatically be cancelled.
<h4>Where should I mail my checks?</h4>
QVC, Inc.
PO Box 1900
West Chester, PA 19380