Applying Split year treatment

I am writing to seek your advice on a potential oversight in my self-assessment tax return for the tax year 2023/24. Here is my situation: I arrived in the UK on 27 April 2023 and began my UK employment on the same day. I resigned from my overseas job on 1 April 2023, but the final salary from this job was paid into my account on 27 April 2023, the day I became a UK resident. Based on advice I received at the time, I understood that since I had resigned before becoming a UK resident, the overseas salary did not need to be reported in my self-assessment. I therefore completed my tax return and paid the tax due without applying the split year treatment. I have recently come across information about the split year treatment and realize I may have been required to apply it due to my circumstances. I want to ensure my tax affairs are in order and comply fully with HMRC requirements. Could you please advise me on the following: 1. Am I required to apply the split year treatment for the tax year 2023/24 based on my circumstances? 2. If so, how should I proceed, given that I have already completed and paid my self-assessment? 3. Do I need to amend my self-assessment to account for the split year treatment, and if so, what steps should I follow?

Hi,
We cannot advise you whether split year treatment applies in your circumstances or not. We can only state that where split year treatment is not applied, the individual is required to declare their world-wide income and capital gains on their tax return for the whole tax year.  
Where split year treatment is applies, the tax return is used to declare all UK income and capital gains for the whole tax year and foreign income and capital gains for the period you were resident in the UK.  
You have up to 2 years after 31 January deadline, to allow you to amend your tax return. You can amend your tax return online or on paper using a tax return and / or the supplementary pages.
Self Assessment tax returns
Thank you.