I am a CJ newbie and I am from Outside USA( living in India) I recently signed up for CJ then I got a mail from CJ asking to complete this form http://www.irs.gov/pub/irs-pdf/fw8ben.pdf whether it is necessary to complete this above form and fax it?
I'm an Indian Publisher, getting CJ checks for the last 2 years and never had to fill any such forms.
Yes, you need to complete that. It's so that the US Government does not withold money for taxes (I believe) - by filling it out, you prove that you're not a US Resident and don't have to pay US Income Tax on what you earn.
This form is must if you are from US or UK or Europe. However, for India it is not mandatory. I have registered without filling in / faxing any forms and am making just $25 per month!!!!