Do you deduct the interest exemption plus tax threshold from interest income to get the total income

Only income earned is investment income thus interest on savings in bank account. Do you deduct the interest exemption of R23800 plus R70700 from the total to establish income e. G R96000 interest income - R23800 - R70700 = R1500 multiply by 18 % taxes due R270

You would say R96 000 - R23 800 which equals R72 200 and then subtract R70 700 and as you say the difference would be taxed at 18%.