You can order a return label for many countries. Go to Product Recycling and select your country. You'll find information on how to order mailing labels. Pre-addressed, postage-paid shipping labels and envelopes are all available at HP Recycle site, however this service is not available in all countries.
For more information about the service in the U.S. please refer to the attached file or call HP Planet Partners at 1-800-340-2445, from 5am-5pm PST.