shahaha

Hi, I have been living and working in the uk for the last 8+ years. I spent 137 days in the UK this tax year. I have been in Spain since mid September and will be starting a new job in Spain from early October, I am also in the process of getting my residency. I want to make sure I understand if I remain to be liable for tax on my Spanish income for the rest of the year/until I become a tax resident here. Am I applicable for the split year treatment? Should I be informing HMRC now or only once I start the new job? I don't have plans to return to the uk in the next 3+ years. Thanks