HMRC Admin 21 Response

Hi shamusj909,
The double taxation treaty between the UK and Guernsey, does not include provisions relieving diviends, interest or royalties.  https://assets.publishing.service.gov.uk/media/5c470999ed915d38b0437c54/2018_Guernsey-UK_Double_Taxation_Agreement_in_force.pdf.  This means that no relief can be claimed for tax paid in Guernsey.
Thank you.

Hi a_s1302,
As long as your savings were earned while not resident in the UK, they will be treated as capital and will not be subject to any tax, when transferred to the UK.
Thank you.

Hi NotSure44,
You would only include the payments made in the tax year.
Thank you.

Hi GrumpyTaxpayer,
Please refer to the following guidance - Pay your Self Assessment tax bill.
Thank you.