IHTM04323 - Property of visiting forces: protection of residence and domicile
No period of duty spent by a qualifying person (IHTM04322) in the UK is to be regarded as a period of residence here for Inheritance Tax purposes. And you should not treat such periods as creating a change of a qualifying person's residence (IHTM13000) for those purposes, IHTA84/S155 (2).
This means that a period of duty spent by a qualifying person will not count towards the long-term UK residence test (IHTM47000).
For periods before 6 April 2025, the legislation confirmed that a period of duty spent by a qualifying person did not create any change in the person’s residence or domicile.