Hi,
Foreign income and gains are only taxed in the UK when they, or amounts ‘in respect of’ or amounts ‘representing’ those income or gains, are ‘remitted’ to the UK.
If foreign income and gains remain offshore and are never regarded as remitted to the UK, the tax charge is effectively deferred indefinitely.
Please see guidance here:
Residence, Domicile and Remittance Basis Manual
If the overseas account contains income or gains which have arisen while t/p is resident in the UK there is a potential tax charge when the account is remitted to the UK.
Thank you.