You will stop incurring fees from the day that you submit your thesis. Your fees will be recalculated so as to be incurred from the start of the relevant enrolment period up to the date of your submission. You will then be able to generate a new invoice for the period you were enrolled prior to submission.
If you have excess credit in your student account after clearing all outstanding debt, you will be eligible for a refund. You can apply for a refund by submitting an Application for Refund and Remission of Fees.