How many of you are tax PROFESSIONALS or consulted one before posting advise on this topic? I did. It amazes me how quick people are to talk out the side of their neck. The W-9 requires a SSN or TIN. Any business that pays out $600 or more to an individual or business in a year can ask for a W-9 and should provide the corresponding documentation at the end of the year. If they are a legitimate operation, there's no reason not to give them a W-9. I don't know why the TIN is unacceptable. That's for them to answer. If you have any doubts about what is proper or not for this type of transaction, consult a tax PROFESSIONAL.