UK-Finland DTA - tax on interest

Hello I need information from you about received foreign savings interest taxed at source to complete my self-assessment correctly. I am a UK citizen who became an employee of an EU Agency in Finland some years ago. According to Article 112 of the UK-EU Withdrawal agreement my tax domicile is UK even if living in Finland temporarily. Below these next questions are the details: 1. Am I UK tax resident for the purposes of tax on foreign interest? 2. If yes, presumably I presume approach the foreign tax authority to reclaim it and would need a document from HMRC for this (and future years). What is that and how to get it? 3. If no, then anyway according to the UK-FIN DTA (HMRC Digest of DTA, April 2018) saving interest is subject to full relief. Does that mean UK will not further tax this already-foreign taxed income? The HMRC International Tax Manual INTM860830 states “any such other income is liable to tax in the normal way” and INTM860870 gives advice to contact a specific HMRC department. The given email address appears to be an HMRC internal one - is there an external email/phone number I can use?. My UK income (including UK savings interest more than 1000 GBP) is above the relevant thresholds for paying UK taxes. I also received foreign savings interest (from Finland) of a few hundred euros which was taxed at source at 30 per cent. I expect also to receive such foreign interest in coming years.

Hi GDC4321,
We are unable to review personal matters in this forum.
For an answer to a personal question of this nature, you would need to contact our Self Assesment helpline;
Self Assessment: general enquiries
Thank you.