Shopify discount codes are not stacking for a Black Friday promotion

Shopify groups discounts into three classes: product, order and shipping. Each discount has a Combinations section where you tick the classes it may combine with. Order discounts are calculated on the subtotal after product discounts have been applied.

Customers can use at most five product or order discount codes and one shipping discount code on the same order. A store can have at most 25 active automatic discounts, and Shopify counts app-based discounts toward that total. When the codes in a cart can't all combine, Shopify picks the best discount or combination for the customer and shows "Some discount codes couldn't be used together. We applied the best combination".

The cause I'd check first is one-sided settings. Your sitewide sale allows order discounts, but the loyalty code was created last year with no combinations ticked, so the pair fails. Both discounts have to allow each other.

The second is the same-item rule. In July 2026 Shopify announced multiple product discounts on the same item, grouped by tags. Shopify's help centre says that needs the Plus plan, and that the tag setup has to be reciprocal: each discount must list the other's tag. On other plans, a 20% collection sale and a 10% creator code on the same jacket won't both apply. Shopify picks one.

Checkout conditions can block a stack too. Combinations only work on orders from the Online Store, the Storefront API and Shopify POS, so a draft order or a sales channel outside that list won't behave like your test. Stores that haven't finished moving off checkout.liquid customisations lose product-with-order and order-with-order combinations. On plans other than Plus, products that are part of a Buy X get Y discount can't take any further product discounts. Custom manual discounts and discounts from the old Scripts API apply regardless of combination settings, which can make the result look random.

List every discount that can be live on Black Friday, including automatic ones, app discounts and evergreen codes like welcome and loyalty offers. For each pair a customer could realistically combine, write down whether you want it to stack. Then set the Combinations section on both sides to match and test the pairs in a new online store checkout.

Look at the order total, not only whether the code was accepted. An order discount calculated after a product discount gives a different number than finance may have modelled. If a discount has a minimum spend, test carts just above and below it with the other discounts applied, so you can see whether the cart still qualifies.

If a creator or affiliate code has to work during the sitewide sale on a non-Plus store, make it an order discount rather than a second product discount. Product with order combining is allowed on eligible stores, and it gives the partner a code that still does something.

If the second discount exists only to add value, don't discount twice. A free gift above a spend threshold raises order value without a second code competing with the first, and it's easier to explain on the product page. Where the logic is too specific for native discounts, such as a hard cap on the total discount per order, it belongs in a discount Function rather than a stack of codes.

For the margin risk of stacking once it works, read Shopify discount stacking: combine discounts, protect margin. For everything else that tends to break the same week, see the Shopify Black Friday problems and fixes guide. If a single code still won't apply at all, start with Shopify discount code not applying at checkout.