This does not prevent you from submitting at a later stage.
If however you do not submit your thesis by your submission deadline and are removed from the Register of Graduate students, this will have implications for your Tier 4 visa.
It is for you to provide a full statement of reasons and it is then open for any party, that is your Supervisor, Department, College and Degree Committee to comment and advise if they wish to support your application.
The final decision rests with the Student Registry.
Details of submission deadlines and arrangements for dissertations can be found at:
Other submission deadlines will be included in your course handbook or available from your course administrator.