The discount codes a buyer enters at checkout.
Three discount types that behave differently
- Percentage — a percentage of the cart subtotal.
- Fixed amount (cart) — a flat amount taken off the cart once.
- Fixed amount (per product) — the amount is multiplied by the total number of items in the cart. A cart of three items gets three times the discount. This is where the mistake is usually made.
In all three cases the discount can never exceed the subtotal; an order is never driven negative.
The code is not case-sensitive
Codes are stored uppercase and what the buyer types is uppercased before it is checked. So summer20 and SUMMER20 are the same code and cannot both exist.
The usage limit is total, not per customer
"Usage limit" is how many times the code may be used across the whole store. There is no per-customer limit — one person can use it repeatedly until the allowance runs out.
Leave it empty for unlimited.
The minimum is measured on the subtotal
It is compared against the items subtotal, before shipping and tax are added. So an order that only reaches the threshold once shipping is counted will still be refused.
The date range is optional
Both the start and end date may be left empty. Before the start and after the end the code is refused, with nothing to disable by hand.
An invalid coupon does not stop the order
If a code is no longer valid at checkout — its allowance filled, its window closed — the order is not refused; it simply goes through with no discount.
So when a customer says the discount was not applied even though the order went through, the code lost its validity between being entered and being paid.