Fix a discount code that will not combine in Shopify
A customer types a second code at checkout and sees an error instead of a bigger discount. This tutorial fixes it on a $100 cart: PANTS20, a 20% product discount on $60 pants, and WELCOME10, a 10% order discount.
Written · Shopify admin, desktop steps · 5 minutes read
The worked example
| Symptom | Discount couldn't be used with your existing discounts |
| Cart | Pants $60.00 + shirt $40.00 = $100.00 |
| Best only | $12.00 off, pays $88.00 |
| After the fix | $20.80 off, pays $79.20 |
Download the planner: discount-combining-troubleshoot.csv (222 bytes).
A worksheet for the two scenarios on the $100 cart: the fix changes what each code saves. The four rows add up to $32.80 of discounts across the two scenarios.
1Read the message
If a customer enters more than one discount code during checkout that cannot be combined, the message displays: Discount couldn't be used with your existing discounts. The second code is not broken: it cannot combine with the discounts already on the order.
2Open the first discount and check Combinations
From your Shopify admin, go to Discounts and click PANTS20, the 20% product discount on pants. In the Combinations section, look at which classes are ticked. Multiple discounts are applied to an order only when the setting on each discount allows the combination.
3Tick the other code's class
On PANTS20, tick Order discounts. That says the product discount may combine with order discounts. One side saying yes is not enough, so the next step matters as much as this one.
4Open the second discount and match it
Go back to Discounts and click WELCOME10, the 10% order discount. In its Combinations section, tick Product discounts. After each discount is set up to combine with the other, a customer who applies both discounts to an order gets them combined automatically.
5Check the pair is allowed at all
Product discounts with order discounts are available only to eligible merchants: your store must not use any checkout.liquid customizations or features, and you must not be using the Licensify app. If your store is not eligible, the codes can never combine, and the best discount for the cart applies instead.
6Save both discounts
Click Save on each discount. The fix only takes effect once both discounts are saved with the matching combination settings.
7Test at checkout
Add the pants and the shirt to a cart, proceed to checkout, and enter both codes. Check that the product discount and the order discount both show, then close the checkout page before payment. Testing without completing a purchase is how you confirm the fix before a customer finds it does not work.
The arithmetic
The product discount applies first; the order discount applies to the revised subtotal.
| Scenario | Subtotal | Product | Order | Total off | Pays |
|---|---|---|---|---|---|
| Cannot combine, best only | $100.00 | $12.00 | $0.00 | $12.00 | $88.00 |
| Can combine | $100.00 | $12.00 | $8.80 | $20.80 | $79.20 |
When the two cannot combine, the best discount for the cart applies: the $12 product discount beats the $10 order discount, so the customer gets $12. After the fix, the product discount applies first and the order discount applies to the revised subtotal of $88.
Held at the counter
One side allowing it is not enough. Multiple discounts are applied to an order only when the setting on each discount allows the combination. A product discount that allows order discounts still will not stack with an order code that does not allow product discounts.
Two product discounts on the same item need Shopify Plus. To combine multiple product discounts on the same line item, the store must be on the Shopify Plus plan. On other plans, Shopify keeps the better one for the customer.
External checkouts do not combine. Discount combinations are not available for checkouts on Facebook, Instagram, Google, or other external checkout platforms. A code that works in the online store checkout may still fail there.
Sources
- Combining discounts — Shopify's help pages: the cannot-combine error message, the both-sides rule, the best-discount selection, the eligibility rules, and the test-your-combinations steps.