What is the actuall purpose of w 9 form?

Form W9 is a request for taxpayer id #, which can be the social security # for an individual or a federal employer id # (FEIN) for a company. It also certifies whether or not you are exempt from backup withholding to the entity that is making payment to you. This form helps clarify your tax status and whether or not you should receive a 1099 Misc for payments made to you for services.