Crisps - £0.75
Drink - £1.00
Giving a total of £3.75
The meal deal kicks in and discounts the transaction to £3.00
What the system does is splits the £0.75 discount across the three items according to the percentage of the value of each component.
Sandwich - 53.33% - dicount £0.40
Crisps - 20% - discount £0.15
Drink - £26.67% - discount £0.20
So the items are reduced as follows:-
Sandwich is reduced by £0.40 to £1.60
Crisps is reduced by £0.15 to £0.60
Drink is reduced by £0.20 to £0.80
The vat is then calculated based on these sales values according to the VAT rate set against each individual component.