Self assessment for building society interest following bereavement

I am trying to find out if my elderly mother needs to complete a tax return for 23-24 based on building society interest, following my father's passing in June this year. There are several building society accounts (not ISAs) in her name, which combined amount to over £10,000 interest in the 23-24 tax year, but she had no other income apart from state pension as far as I'm aware. My understanding is that she will need to register for self assessment and complete a tax return for 23-24, even though my father was still alive during this period (he managed the family finances so my mother is unsure).

Hi,
If the untaxed savings interest is more than £10,000 then this is Self Assessment criteria and a tax return will be due.
Your mother can register at Register for Self Assessment if you are not self-employed
Thank you.