Where can I find my Playstation 3 id?

Question

I can find the serial number on the back and i know that's not it, so where can I find it.

Answer 1

If you mean the gamertag type id you use for games, logging onto the PS network, etc, then you choose your own when you create it (go to the last option on the XMB (cross-media bar) and select 'sign up').
All the info you need for registering should be on the back of the console.

Answer 2

IT ON THE BOX 3RD ONE DOWN ON THE SIDE