Questions about self assessment tax return

To HMRC admin I came to uk with bno visa from hong kong, I haven't been working for couple years and I am currently unemployed, I have gain approximately £90 saving interst a whole year from my hong kong bank account and that's the only foreign income i have, do I need to do the self assessment tax return? I have already done the self assessment tax return check on the government website and the results said that I don't need to, but I have been told that as long as I have foreign income I have to do one Best regards

Hi 

How can the original investment amount be brought into the UK?  It is invested.  It is only when the investment is disposed of that a gain may arise.  
If you are UK resident when this happens, it may result in a capital gain, which may be taxable.

Thank you