Tax credit for sale of flat in 26AS as power of attorney

Hi, we have given our land for development , developer has given power of Attorney to land owner ( my father ) ... Now builder has completed building and he sold one flat (his flat) for 51 lakh , since my father has power of attorney Registration done by using PAN of my father , transaction took place in November 2020 and entry reported in May 2021,  now when I am checking my father's 26AS annual information summary I can see entry of 51 lakh , since my father done Registration as a Attorney and not earn even single Rupee in this transaction , what should we do for tax credit entry in 26AS , we have not received any notice yet from IT department and not file IT return either since in 2020-21 my father income was only 150000...

1) Kindly assist what to be done now

2) and what to be done if in future IT department demand to pay capital gain tax or send Notice ??

Thanks