Clarification Needed on "Untaxed Interest on Savings and Investments" Calculation and Source

I have noticed that gov.uk has already calculated my "Untaxed interest on savings and investments." However, I'm unable to locate the details regarding the calculation and the source of this information. As a result, I cannot identify which financial institution provided this data to gov.uk, making it difficult for me to accurately complete my tax return. Could you please guide me on how to find this information within my Personal Tax Account or provide further clarification on how the figures were determined? Or directly provide me the source and calculation? Thank you for your assistance.

Hi angelapowuk,
You will need to contact for a breakdown of the details held by HMRC here:
Income Tax: general enquiries
Thank you.