A remark about discount calculating.
How exactly do you calculate it?
Code:
if InvoiceTotal is > £200, then 5% discount, >100, then 2.5 % discount, else, no discount
Does this mean that when invoice sum is 200, then the customer will pay 200 - 0.025*200 = 195.00, and when invoice sum is 201, then the customer will pay 201 - 0.05*201 = 190.95 (what is 4.05 less than 1.00 cheaper invoice)
,or when invoice sum is 200, then the customer will pay 200 - 0.025*(200-100) = 197.50, and when invoice sum is 201, then the customer will pay 201 - (0.025*(200-100) +0.05*(201-200)) = 198.45 (what is 0.95 more than 1.00 cheaper invoice).