Stacking rules with Shopify discounts
Understand how free gift tiers stack with each other and with Shopify discount codes.
Free Gift + Free Shipping
Stack natively. Both can apply on the same order with no special configuration.
Free Gift + customer discount code
Depends on the code's combination settings in Shopify admin. Open Discounts → (your code) → Combinations and explicitly allow it to combine with product discounts and shipping discounts as needed.
Multiple Free Gift tiers
Only the highest qualified tier of each reward type applies, unless you explicitly enable cumulative tiers. This prevents "infinite gift" loopholes.
Common gotcha
If a customer reports their code "won't apply", the cause is almost always a combination rule in Shopify, not the app. Check Discounts → Combinations first before debugging the app.
Use Validate Discount (in the app) to simulate a cart against your full setup and see exactly which discounts apply.