Shopify calculatescorrectly, but the ERPstill books thediscount wrong

In short

In the store, every discount was right. In the ERP, some discounts never arrived at all, others showed up as a separate voucher line instead of on the product. The reflex would have been to rebuild the store. Instead, we tested where the error really happens, and it wasn’t in Shopify.

The case

A wholesaler uses different discount types: volume discounts, “Buy X, get Y”, discount codes. In the cart and in checkout, everything calculated correctly. Orders were transferred to the ERP via a connector, and there things looked different. Some discounts were missing, others appeared as a separate line item. For accounting, that meant manual work on every affected order.

The cause and how we found it

“Shopify shows it correctly” doesn’t mean the record is processed correctly. A discount can sit in a Shopify order in different ways: directly on the product line, spread across the whole order, or as a code. Every connector and every ERP reads these types differently.

Our approach:

1. Same cart, different discount types. We created identical test orders and only changed the discount type.
2. Before-and-after comparison. For each order: what’s in Shopify, what arrives in the ERP?
3. Spot the pattern. Discounts on the product line arrived cleanly. Order-level discounts were either not imported by the ERP or imported as a separate line item.
4. Narrow down the fault. That made it clear: the logic in the store works, the translation in the ERP doesn’t.

With this finding, the ERP vendor could fix things in a targeted way. Without it, we would have rebuilt discounts in the store that were actually right.

Your takeaways

• The visible spot is rarely the cause. With errors between two systems, test the boundary first, then repair.
• Workarounds in the store are dangerous when the error actually lies behind it. They shift the problem and make it harder to find.
• Give the ERP vendor a concrete example. Discount type, order number, what’s in Shopify, what arrives in the ERP. Nobody can work with “it doesn’t work”.
• Test new discount types before you go live with them. One test order through the whole chain, all the way into accounting.

Seeing mismatches between your store and your ERP? In our audit, we find out which side the error is on before anyone rebuilds anything.