Hi,
As a resident, who is not domiciled in the UK, you are required, by default, to declare your world-wide income using the 'arising basis'.
If your overseas interest is less than £2000 and no tax is deducted from it, you can declare the interest in box 3 of SA100, so that it can be included in the tax calculations.
If you are not remitting the interest to the UK, then you are electing to use the 'remittance basis', which requires the completion of SA109, to claim the remittance basis and declare the unremitted income.
Have a look at Section 9 of RDR1, regarding the remittance basis. Exemption for small amounts of foreign income would not apply for overseas interest in excess of £100.00.
Residence, domicile and the remittance basis: RDR1
Thank you