To prove income for student loan requests, send a copy of your tax return, whether it's a 1040, 1040A or 1040EZ.  If you send only this, they will often comeback and ask for copies of your W-2s, so you may save time by just including copies of any W-2s along with the return.  Make sure you sign the return copy before you send it, at the bottom of the 1st or 2nd page, or they will return it asking for a signed copy.