Well i wanted to sing up with some companies but some of them ask to choose form for the tax. I have no idea what to choose. Im an non-us individiual living in Europe. The options in Azoogle and some other similar is: Form W-8BEN, Certificate of Foreign Status of Beneficial Owner for United States Tax Withholding. Form W-8ECI, Certificate of Foreign Person's Claim for Exemption From Withholding on Income Effectively Connected With the Conduct of a Trade or Business in the United States. Form W-8EXP, Certificate of Foreign Government or Other Foreign Organization for United States Tax Withholding. Form W-8IMY, Certificate of Foreign Intermediary, Foreign Flow-Through Entity, or Certain U.S. Branches for United States Tax Withholding. To me it seems W-8ECI is the one. But after i choose it there is spot to put: U.S. taxpayer identification number, (required - see instructions) : * and the Foreign tax identifying number, if any (optional) is just optional. I have my european tax id, but i dont have the 'U.S. taxpayer identification number' and dont know what to do wit hit. What to choose there?