Self Managed Strata in SA

HI one of my block of units is self managed. We do not complete a tax return, as we do not receive any interest/income.
If we were to change banks and get some interest say $50 per year, do we have to register as a business, fill out Bas forms and complete a tax return each year.
I tried to ring the ATO today, it was a 40 min wait.
Thanks
 
Top