Iankoko Chan

I moved to the UK in July 2021. I ended my HK employment in May 2021 and started UK employment in Oct 2021. So, I am qualified for split year treatment for FY21/22 under case 4. Question 1: Does the split year treatment applied to my case automatically? After Oct 2021, except the UK Salary, I only have foreign dividend and interest income less than £500. My UK employer filed PAYE for me and I did not use up all the personal allowance. Question 2: Under my case, do I need to file self assessment tax return? Question 3: If I need to apply split tax treatment and self assessment for FY21/22 but I did not do it before 30 January 2023, are there any penalties if I do it now and it seems I don't have to pay UK tax on my foreign income.