Hello, I am Keith, one of the experts on Just Answer, and pleased to be able to help you with your question.
You will have to file on paper, and you have 30 days from HMRC's request for a return for 10/11. You will have to approach your tax office for them to send you a form if they have not already done so. Alternatively you may be able to dig one out from the Government Archive viz:
I do hope that you have found my reply of assistance.
Thank you for your support.