Submitting Return online for elderly relative

I have authority to act on behalf of my mother with HMRC. She has now moved under SA . I would like to be able to do this online but she no longer has a valid passport, driving licence or other way to verify identity. Is there a way I can set up an online record for her, to be able to do her return online in future years.

Hi,
While you may not be able to file your mother's return online if you do not have any of the necessary forms of identification for her, we may be able to offer additional support.
Contact us by webchat or phone via:
Self Assessment: general enquiries and we can advise you further.
Thank you.