Co-signed student loan and paid interest. Not on 1098-E. How to enter in turbo-tax?

You can report interest paid on a school loan that you co-signed as long as you are claiming the student as your dependent. 

A 1098-E is not needed as long as you have documentation of the interest paid and that you are a signer on the loan.

If the student is not your dependent, and the student is filing as a "non-dependent" the student may be able to claim the interest payments. 

According to the IRS:

"Interest paid by others. If you are the person legally obligated to make interest payments and someone else makes a payment of interest on your behalf, you are treated as receiving the payments from the other person and, in turn, paying the interest."

IRS Pub 970