Use a small test matrix and record the intended result before running each case. That makes an unexpected saving or rejected code easier to diagnose.

Start with the actual discount classes

Shopify distinguishes product, order and shipping discounts. Combinations depend on eligibility, the items in the cart and the combination settings of the discounts involved. Do not assume two promotions will combine because each works by itself.

Also distinguish an existing sale price from a discount code. A code can operate on an already reduced selling price, so checking only the code's displayed percentage can miss the true reduction from the original price.

Build the matrix before the launch rehearsal

For every row, save the discount names, basket contents, destination, expected total and actual total. Include the timezone used for scheduled start and end times.

Understand the arithmetic you are testing

One important distinction in Shopify's documented rules: eligible percentage order discounts are calculated against the original subtotal. For example, two such discounts of 10% and 20% on $100 produce $30 in combined savings, not a sequence that leaves $72. Product-then-order combinations follow a different sequence. Verify the rule for the classes you actually use rather than applying this example to every promotion.

Treat the example as an explanation of the documented combination behavior, not a suggestion to offer both discounts.

Rehearse safely

Choose a Shopify-supported testing method and account for its effect on a live store. Shopify warns that customers cannot place live orders while payment providers are in test mode. Plan that test deliberately and confirm the live configuration afterward.

Check the order record and customer-facing message, not only the cart subtotal. Give support a short explanation of each intentional exclusion and a route to escalate a basket that behaves differently.

Launch gate: Do not advertise an offer until the highest-risk rows have an expected result, a passing test and an owner.

Merchant discussion: Which combination has caused the most confusion in your store: welcome codes, loyalty offers or shipping discounts?

Continue on Eggflow Blog

Extend the discount matrix into a complete purchase rehearsal with the BFCM store stress test on Eggflow Blog, especially its offer-interaction and launch-acceptance checks.

Sources and further reading

Platform rules checked October 31, 2026; eligibility and features can change.

• Shopify: combining discounts
• Shopify: placing a test order

Browse the BFCM 2026 guide series.