We're having a major problem getting Sage Accounts to recognize all basket items submitted to MySagePay via Protocol 3.0 (https://live.sagepay.com/gateway/service/vspform-register.vsp ) using the OpenCart Sagepay Server payment module modified to include either Basket or BasketXML fields. In particular any items that are discounts are not picked up and cause amount owings on ledgers as the amount the customer has paid does not add up to the basket items total.
We were told to use the original colon-delimited Basket field, but this has no means of specifying if an item is discounted other than to submit it as a negative value, which is ignored by Sage Accounts.
Further to this discount items submitted to MySagePay using a correctly formatted BasketXML field also fail to appear on payment details (though the total amounts balance).
We were also advised to ensure that ProductSKU's for basket items submitted to MySagePay matched exactly the SKUs used in Sage Accounts, however there is no way to specify an SKU for a discount item.
I am pretty certain we've done all we can from the website-to-MySagePay end, so how do we ensure that shopping basket contents including discount items are correctly picked up by Sage Accounts from MySagePay?
Basket XML is not supported by Sage Accounts and nor does Sage Accounts pick up negative values like you said. Until Sage Accounts adopts XML there is no way to pull through a discount.