Here's a posting to thread in a AnandTech forum on the subject.
"I had the same question so I shot an email to NewEgg a couple of days ago.
Here is their response;
Dear xxxxxx,
Thank you for your patience and understanding; our Product Support has
informed
us that you will need to send the original UPC along with a COPY of the UPC
and
the invoice, with both forms filled out. Also be aware that they must be
sent in
the same envelope, and BOTH offer numbers must be clearly written on the
envelope as well.
Thank You,
ext105
@newegg.com
Customer Service Support
ph: 800-390-1119
fax:909-395-8907
I saw a post with a similar reply on another forum from Soyo to the same
question however, Soyo never responded to an email that I sent to them. "