Power of attorney self assessment

Hello, 2 years ago I sold my mother's home as she had to go into a care home. I used a financial advisor and invested a bulk of the money and the rest I keep as cash to pay for her care. She has made some money from her investments, and I have the power of attorney to manage her accounts. As I am employed I have never had to do a self assessment form tax, but have realised this may be something I need to do on her behalf? She is not a UK resident but does have indefinite leave to remain, and has lived here for 45 years. Can anyone advise?

Hi
As she has been here for 45 years, she will be classed as UK tax resident.
Please see guidance at :
Self Assessment tax returns on who needs to file a return.
Thankyou.