On an F-1, being in the country, under 5 years, you ordinarily would not be a resident of the United States (just remember to file IRS form 8843). so you should file form Form W-8BEN, Certificate of Foreign Status of Beneficial Owner for United States Tax Withholding. This will cover payments of interest, dividends, and capital gains on marketable securities.Form W-9, Request for Taxpayer Identification Number (TIN) and Certification is for US citizens and residents. Since you are on an F-1 visa, you are neither.Form W-8ECI, Certificate of Foreign Person's Claim That Income Is Effectively Connected With the Conduct of a Trade or Business in the United States is for people who are earning u201ceffectively connected incomeu201d (typically self-employment) income. Your broker probably isnu2019t paying you this.RSUs are beyond the scope of this question.Also, if youu2019re working as an employee, please ensure you have the legal right to so. This is not a tax question.