Sandwich £2.00

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.