Amazon and Shopify don't handle partial refunds on multi-product orders the same way. If your Amazon order has more than one SKU/product, a partial refund issued in Shopify can be rejected by Amazon when it doesn't include enough information for Amazon to know exactly what's being refunded.

Why it happens

Shopify lets you split refunds freely — refund one SKU/product on Monday, another next week, and so on. Amazon's refund API expects a single refund submission to describe every affected SKU/product with its own quantity and amount. If the app submits a partial refund without the per-SKU breakdown Amazon expects, Amazon rejects it.

This is most common when:

• An order has two or more SKUs/products, and you refund only one.
• A single SKU/product has a quantity greater than 1, and you refund only some of the units.
• The refund amount doesn't break down cleanly to specific SKUs/products (e.g., a partial dollar refund applied across the order).

Fix it

On the Orders page, find the row with the Failed Refund status and click on Failed Refund. In the Failed Refund dialog:

• Tick only the SKUs/products you actually want to refund (each one with the correct Refund Inventory quantity).
• For each ticked SKU/product, set the Refund Reason (Amazon) and the per-SKU Refund Amount that matches what Amazon captured for that line.
• Leave SKUs/products you don't want to refund unticked — they stay on the order.

Click Confirm. The app sends Amazon a per-SKU refund that Amazon can process.

Tip

For multi-product orders, prefer issuing the Shopify refund per SKU/product rather than a flat dollar amount across the order. That way the app has clean SKU-level data to forward to Amazon.