Nowhere. The W-9 form is the request for taxpayer identification. It has absolutely no income or expenses reported on it what-so-ever. Whomever requested the W-9 from you is responsible for issuing you the appropriate tax reporting document come tax filing season. That document could be anything from a W-2, 1099-MISC, K-1, or any number of the other forms used to report taxable income to the person or entity responsible for paying taxes on it.
