Norway and UK tax liability for UK residents

Can you advice with which country should be used to claim tax relief for a person who is tax resident in both UK and Norway? All tax residents of Norway are subject to tax on their entire income (including foreign income) and wealth with the tax year running from 1 Jan 2023 to 31 Dec 2023 and tax returns to be completed by 30 April 2024. A tax resident in UK will have their tax timelines from 6 April 2023 to 5 April 2024 with tax returns to be completed by 31 January 2025. As there is always a time lag where the person has already paid Norwegian tax upfront and cannot claim relief as the UK tax timelines are almost one year later for the same time period, Can you advice how should the tax relief be claimed in such cases? Thanks for your advice.

Hi,
There is no need to apportion your income.  Treat your income from 01 Jan to 31 Dec as the same as 06/04 to 05/04, when completing your self assessment tax return.  You will need to review the tax treaty that exist between the UK and Norway.  It is reciprocal.(Norway: tax treaties).  Please have a look at help sheet HS302 for guidance on dual residency:
(Dual residents 2024 (HS302)
Thank you.