For savings interest this is classed as 'investment income' if someone receives more than £10,000 of investment income they are required to submit a Self-Assessment tax return to declare this.
If you are not required to complete a tax return, there is no set form for declaring investment income.
Financial institutions will declare savings interest that is not held in ISA accounts to HMRC, and we will update our records accordingly.
If you wish to do this before then, you will need to provide details of the accounts that you receive interest from by contacting our Income Tax team by telephone or in writing.
Income Tax: general enquiries