I changed my address and the bank sent me a Form W8-BEN.
Do I have to fill it and send it to them?
Go ahead and fill out and send the form to the bank. You may receive bank interest from which withholding will be taken unless you declare exemption by returning the form. These are some instructions for Form W8-BEN from the IRS at:
" Form W-8BEN, Certificate of Foreign Status of Beneficial Owner for United States Tax Withholding
Give this form to the withholding agent or payer if you are a foreign person and you are the beneficial owner of an amount subject to withholding. Submit Form W-8BEN when requested by the withholding agent or payer whether or not you are claiming a reduced rate of, or exemption from, withholding."