shopify discount codes stacking unexpectedly

The actual problem

Multiple active percentage codes combine at checkout and erase margin on paid traffic.

Do this

1. List every active discount in Shopify Admin → Discounts.
2. Flag any code with value ≥10% that allows combining.
3. Disable legacy seasonal codes still marked Active.
4. Re-test checkout with two codes; confirm rejection or single-apply.

Tools for this job

• Tillkiln

  Automated scan for stacking + dead links

• Shopify Discount Docs

  Official combine rules

Related intents

• /q/shopify-guest-checkout-disabled
• /q/stripe-fee-ratio-too-high