Reduction in set off

You don't have an option but to apply the ratio :

STEP 1 :   The ratio will be the ratio of the sales of tax free goods and taxable goods

STEP 2 :  Take the total purchase value for all the goods purchased * (the above ratio)

The value obtained in STEP 2 will be multiplied by 3% to get the retention value which will be subtracted from the total set off available

Ok ....

Thnx a lot ...........