Hi,
Claiming split year treatment requires the completion of a Self Assessment tax return (SA100), which requires a UTR.
You can register for Self Assessment and a UTR here:
Check how to register for Self Assessment
Claiming split year treatment for 2023 to 2024 also requires the completion of SA109, together with SA100. They will be available from 6 April 2024 onwards here:
Self Assessment tax return forms
Both the SA1010, SA109 and any other supplementary pages, should be posted together to:
Self Assessment
HM Revenue and Customs
BX9 1AS
United Kingdom
If they are being posted from outside of the UK, you should address them to:
Benton Park View
Newcastle Upon Tyne
NE98 1ZZ
United Kingdom
Thank you.