Hi Yevhen,
Where split year treatment applies, there will be two periods in the tax year.
One where you are not resident for tax purposes and the other where you are.
In the not resident for tax purposes period of the tax year, you would only declare any UK income and capital gains that arise in that period.
In the other period, where you are resident for tax purposes, you will declare all of your world-wide income and capital gains on the tax return.
We can only provide general advice in this forum.
If you require more detailed information, you will need to contact our Self Assesment helpline on 0300 200 3310 or contact our webchat facility here:
Self Assessment: general enquiries
You also have the option to seek the advice of a professional.
Thank you.