Purchase amount is not the amount I paid
The main reason for this happening is that some retailers do not pay cashback on VAT, other types of taxes or delivery charges and this is possibly why your purchase is amount is lower. Curry's is an example retailer who does this.
You can check your order confirmation email or invoice and this will usually be broken down, so you can see how much your purchase was minus any tax or fee. This website calculates the VAT for you in instances where this isn't so clear on your emails: http://www.vatcalculator.co.uk/
The cashback amount is not what I'm expecting
When you make purchase, some retailers will initially track your purchase at a lower cashback amount and then uplift to the correct amount generally after 2 weeks of the purchase being made. Example retailers are Curry's, World Remit and Mobile Phone Retailers. We appreciate this is confusing and annoying and we are closely working with all partners to make the experience better for you.
If you made a purchase from another type of retailer it could be that something went wrong in the purchase journey and we would need to look into that for you. Please contact our support team via the messenger and they will happy to help!