It's best to submit a withdrawal/interruption request during the academic year you want to be withdrawn/interrupted from.
Once you receive an invitation to register for the upcoming year, you can submit a request to withdraw or interrupt if you aren't due to submit any resits or reassessments. If you do have resits or reassessments, follow the information on your result letter or from your Faculty.
If you have exceptional circumstances and need to interrupt/withdraw for next year during the current academic year, please make sure you let the Retention & Success Office know when you submit your request.