Yes, if you are using TurboTax CD/Download, he can
use any returns you have left over.
If you are using TurboTax Online and have the
Standard 8 return package, then he can use it to prepare his return, but he
must do it in the same account as you used to create yours.
If you are using TurboTax Online but don’t have
the Standard 8 return package, then he can create a new return in TurboTax
Online, but he will be charged separately. He can also create his own account.