diff --git a/order/order.go b/order/order.go
index c248013..1d71f54 100644
--- a/order/order.go
+++ b/order/order.go
@@ -39,6 +39,8 @@ type Created struct {
 	OrderID        string `json:"order_id"`
 	OrderReference string `json:"order_reference,omitempty"`
 	CartID         string `json:"cart_id,omitempty"`
+	// CheckoutID links the originating checkout grain (wire-safe addition).
+	CheckoutID     string `json:"checkout_id,omitempty"`
 	Country        string `json:"country"`
 	Currency       string `json:"currency,omitempty"`
 	CustomerEmail  string `json:"customer_email,omitempty"`