Hi Miranda Lim,
The unremitted income declared from a previous tax year now being transferred to the UK, will be taxable in the tax year in which it is transferred to the UK and must be declared in a Self Assessment tax return.
Savings / earnings generated outside of the UK, in tax years that you are not resident in the UK, would be considered capital and not taxable when transferred to the UK.
Please have a look at the guidance on remittance basis at RDR1:
Residence, domicile and the remittance basis: RDR1).
Thank you.