Extending your study
If you have been granted a concession to extend your PhD programme and you need more time in the UK to complete it, you will need to request a new CAS and extend your current Tier 4 visa. You can apply to extend their visa in the UK.
Undergraduate students given permission to repeat a year of their programme can also request a new CAS before continuing study, but can only apply for a new visa from outside the UK.
Postgraduate Taught students cannot normally apply for more time on their visa if their programme end date has been extended.