TSEM10265 - Non-resident trusts: trustees’ chargeability: Capital Gains Tax
If the trust is non-resident throughout the tax year, the trustees are not chargeable to Capital Gains Tax on any trust gains made in that year. But the settlor or beneficiary may be taxable on capital gains - see CG38200SUBC.
If the trustees are resident for any part of a tax year, gains arising at any time in the tax year are chargeable to Capital Gains Tax. There is no split year treatment. For example, where a UK resident trust becomes non-resident during the year there may be an exit charge (TSEM10270).