Hi,
Any source of income from overseas, whether remitted to the UK or not, regardless of what it is or how much it is, is a criteria for completing a Self Assessment tax return.
If you are in a position to claim for the remittance basis, being UK resident but not domiciled, you will still be required to complete a Self Assessment tax return. You can see the guidance below for more information on the remittance basis:
Guidance note for residence, domicile and the remittance basis: RDR1
Thank you.