Test the discount on its own with a cart that meets every condition. If it works alone but fails with another offer, investigate combination settings and eligibility. If it fails alone, start with the code, dates, customer, products and minimum requirement.
Keep one reproducible cart
Record the exact code and displayed error, product variants, quantities, selling plan, customer/login state, market, currency, shipping destination and time. Use a fresh checkout to compare tests. Changing several of these at once makes it difficult to identify the rule responsible.
| Observed message or symptom | Check next |
|---|---|
| “Enter a valid discount code” | Exact spelling, whether the code exists, active dates and usage limit |
| Code is not valid for the cart’s items | Included variants/collections, quantities, minimum spend and purchase type |
| Codes cannot be used together | Both discounts’ allowed combinations, discount classes and merchant eligibility |
| Works for one buyer but not another | Customer eligibility, one-use limits and whether the same account is signed in |
Shopify can vary the wording by checkout context and language. Preserve the actual message in your diagnostic notes rather than treating a familiar sentence as the diagnosis.
Check the discount record systematically
- Confirm the active window in the store’s timezone and remaining uses.
- Compare the qualifying subtotal/quantity and selected products with the cart. Check how other discounts change the calculation.
- Check eligible customers and whether subscriptions or one-time purchases are included.
- Confirm the relevant market/channel context and the actual currency amounts. Do not assume a threshold displayed in one currency has been interpreted correctly elsewhere.
- If two offers are involved, inspect each discount’s combination settings. Permission on only one offer is not enough.
Understand combination limits
Shopify distinguishes product, order and shipping discounts. Eligible combinations depend on the classes and setup; multiple product discounts on the same line item require Plus. An automatic discount can also affect which combination wins. Read the current rules rather than promising that any two codes can stack.
Use a small test matrix: code A alone, code B alone, A and B together, then the same cases with an active automatic offer. Keep the cart and customer constant. If a discount is created by an app, record the app and rule as well as Shopify’s visible record. Do not delete a live app or custom function as a diagnostic shortcut.
Scope the fix from evidence
A configuration error may need only a settings change. A requirement outside native rules may need app configuration or custom discount work. For Shopify discount troubleshooting, send the test matrix, rule you want and redacted screenshots of the error and settings. Our quantity-discount guide addresses a different question: counting quantities across variants.
Sources: Shopify combination rules; Shopify discount errors and eligibility.