Split Year Treatment

I have reviewed the rules and understand that I am qualified for the split year treatment. My questions are: (1) does the split year treatment apply automatically if I am qualified to this? or will the split year treatment only apply to me after I have applied for it through the self-assessment form or other methods? (2) when I fill in the self-assessment form, whether I need to report income for the whole tax year or only report the inform for the UK part of the year? Thank you.

Hi

Split year treatment can only be claimed by completing a self assessment tax return.  You need to use a paper tax return (SA100) to be able to submit SA109 and any other relevant supplementary pages.  
If you are able to verify your identity, you can buy a commercial tax return that include SA109 built in and send this online.  
In either case, the whole tax return must be submitted in the same format, either on paper or online.

Thank you