The serial number and license number are the same. If your on1 product is still installed and running you can locate the serial/license number inside of the product. Open the product as a stand alone application. You will need to locate the "About" window. If using Windows this is under the Help menu, Mac users want to look under the Perfect Photo Suite menu at the top. When you select the product from this list, the About Box will show the license number.
If you have purchased directly from on1, Inc. you should have received the license number in your confirmation email after purchasing. If you need help locating your license number still, please contact Customer Service. Please email us from the same email you purchased with.