The regular W-9 form is used most often and also related to as the W9 form or Form W9. You can use it for a lot of purposes but most often it is used to get the name and address and Taxpayer ID number and Certification of a tax paying American citizen who is a sole proprietor.
An example of it's use would be a person who works as a freelancer performing music in a restaurant, concert, venue etc.
Instructions for the Requester of Form W-9The requestor information pack is a 4 page package.
Created by the IRS it is about what a person needs to know before asking for and filling out a W-9 form.
The W-9SIt is a Request for the Student’s or Borrower’s Taxpayer Identification Number and Certification. This is a two paged form and has less information on it than the regular W-9 form has. It asks for the "Student or Borrower Identification", "Student Loan Certification", etc. It is an easy form to understand and fill out.
This is the form that a certain foreigner would use as they sometimes can not use the W9 form. If you think this applies to you then download the form and instructions to read them for info.
The next two W-9 related forms are in Spanish:
W-9(SP)"Solicitud y Certificación del Número de Identificación del Contribuyente".
It is the Espanola or Spanish language version of the W-9 form or Formulario W9 .
This is the instructions for the requestor of the form W-9 in Spanish.
I would reccomend that you use the website www.PrintW9.com for a lot of info concerning these tax forms.