Why they usually stack
Think of a checkout as two separate steps.
- Work out what this costs. Discounts, promotions and offers happen here.
- Take the money. Gift cards, bank cards and wallets happen here.
A discount code belongs to step one. A gift card belongs to step two. Since they are not competing for the same slot, both can apply.
The order matters
Apply the discount first, then the gift card.
Applying the gift card first works at well-built checkouts, which recalculate correctly. At badly built ones it can mean the discount comes off the part you were going to pay by bank card, so more of the gift balance is consumed than necessary. Same total, worse outcome for you.
The sequence that always works:
- Fill the basket.
- Apply the discount code.
- Apply the gift card.
- Pay the rest.
When it will not work
- The discount excludes gift card payment. Rare, but it exists, usually on deep promotions.
- The gift card is really a voucher. Vouchers behave like payment instruments and frequently do not stack with promotions. The difference is explained in gift card, gift code, voucher, promo code.
- The basket contains excluded items. Marketplace stock, other gift cards, subscriptions.
- The checkout takes one payment method only. Small shops, mostly.
Two discount codes together
Almost never. Checkouts accept one promotional code per order as a rule. Where a second field exists it is usually for something structurally different, like a loyalty reward.
Two gift cards together
Usually fine, often capped at two or three payment instruments. Loading balances onto an account first sidesteps the cap where the brand supports it.
Checking it actually worked
Before confirming, read the summary:
- Discount line present and the amount you expected.
- Gift card line present.
- Remainder on the bank card equals the difference.
If the numbers do not add up, remove everything and reapply in the right order. Unpicking it after the order is placed is much harder.