Yes, you do. If you plan on earning more than $600 (or already have), we need to issue you a 1099 form at the end of the year. Uncle Sam waits for no one :)
This simple form can be submitted online (securely), and you can find that form, here: http://thesuperaffiliatenetwork.com/substitute-w9/
In order to fill it out, you must be logged into the members area.
If you are an international affiliate, our Accountant recommended that you fill out this form and submit to our customer support desk: