If you have a NUS Extra card but no railcard you can get 25% off tickets with TPE - see link for details.
There are no age restrictions.
The 25% off discount is only available when booked via the special TransPennine Express web page accessible from the NUS extra website. You need to log in to NUS Extra to access this page. When selecting your train journey you must flag that you are an NUS extra card holder in the Railcard drop down box.