If you are an international affiliate, filling tax froms is quite a hassle especially when you are not sure which one you should be filling in. But most of the affiliate networks such as CJ and Linkshare requires you to fill in one.
You may receive a W9 form to complete if you are hired to perform services for another company but are not an employee. If the company is required to file a return, it must obtain your Taxpayer Identification Number in order to file. People who are asked to fill out W9 forms include freelancers, consultants and independent contractors.
The IRS generally subjects foreign people to United States tax at a rate of 30 percent on income they receive from domestic sources. IRS Form W8-BEN exists to allow certain persons to claim eligibility for reduced rates or exemptions from these taxes as residents of a foreign country with which the United States has an income-tax treaty.