How is good/bad is Prince Harry and Meghan Markle's timing when it comes to tax?

Tax-wise, six years away could be a very important number. The UK’s temporary non-residence rules generally target people who return within five years, so if Harry and Meghan have genuinely been non-UK resident for more than that, certain gains realised while abroad may escape being pulled back into UK CGT on their return. However, once they become UK tax resident again, future gains on worldwide assets can fall back into the UK tax net — and six years away is not enough to qualify for the new four-year foreign income and gains regime, which requires 10 consecutive years of non-UK residence. So if major disposals were planned, timing them before UK residence resumes could make an enormous difference.

Six years could represent favourable CGT timing, but only in relation to gains they have already realised while genuinely non-UK resident. If each of them has been non-resident for more than five years, the temporary non-residence rules should generally no longer claw those gains back on return, although UK land remained within the UK tax net throughout. There is no automatic CGT reset on coming home, however, so assets sold once they are UK resident may be taxed on the whole chargeable gain, while their worldwide income and gains would normally also come within scope, subject to any available split-year treatment. Six years is also too short for the new four-year foreign income and gains regime, which requires ten consecutive tax years of non-UK residence, so the simplest answer is: potentially good for disposals already made, considerably less attractive for assets still held.