taxation for UK resident with cantonal (state) income in Switzerland

I worked for 7 weeks as a Maths teacher in a state school in the Canton of Aargau in Switzerland last summer. I am a Swiss citizen regularly resident in the UK and deriving my usual income from UK-based employment and some self-employement (I do self-assessment as a result of the self-employment.) I spent most of the remaining 45 weeks of the 2022/23 tax year in the UK (minus a few days here and there for holidays.) I am struggling to fully understand how the provisions of the UK/Switzerland double taxation convention apply to me. 1) according to article 19, remuneration paid by a contracting state or a political subdivision thereof (my income was paid directly by the cantonal administration of the Canton of Aargau) is taxable only in Switzerland. The caveat (b) for work performed in the other contracting state does not apply since I performed my teaching duties in Switzerland and was never in the UK during the 7 weeks of my employment there. I was taxed at source in Switzerland and the cantonal authorities requested details of my total UK income so the tax rate applied by the Swiss authorities to my Swiss income takes my total income into account. 2) article 22 stipulates that tax paid in Switzerland is allowed as a credit against any UK tax computed by reference to the same profits. If I understand article 19 correclty, no UK tax should be computed by reference to the same profits since article 19 says that my Swiss income is only taxable in Switzerland. If so, article 22 does not apply to my case? I am now at a loss as to how to declare this income in self-assessment. Is it the case that due to Article 19, I should not be declaring the income, or at most just mention it in "Any other information", quoting Article 19 to explain why I did not include it in my declared income? Or should I on the contrary declare the income, quoting Article 19 and let HMRC deal wth how Articles 19 and 22 apply to my case?

Hi,

As a UK tax resident you are liable on your worldwide income and need to declare the income from Switerland. You then claim Foreign Tax Credit Relief for the tax paid there which covers the UK tax due on this income so no additional liability is actually due.

Thank you.