RFIG21540 | Statutory Residence Test (SRT): Temporary non-residence: Start and end dates for period of temporary non-residence
From HM Revenue & Customs · Residence and FIG Regime Manual
An individual’s period of temporary non-residence starts from either:
the date immediately following the last residence period in which they were solely resident in the UK (referred to as period A)
if split year treatment applies to the individual, the date following that on which the last residence period for which they had sole UK residence ends.
The period of temporary non-residence ends on the day before the date of the start of the next residence period for which an individual has sole UK residence.