Marketing & discounts
Cart (sales) rules, catalog price rules, and coupons.
Two complementary rule engines drive promotions.
Sales rules (cart)
Sales rules apply at the cart level: percentage/fixed discounts, free shipping, buy-X-get-Y, optionally gated by a coupon code and conditions (cart total, customer group, items). They affect the quote totals.
Catalog price rules
Catalog rules adjust product prices in the catalog itself (e.g. "20% off all items in brand X"), independent of the cart. They're evaluated against product attribute conditions.
Conditions
Both engines use a condition builder referencing product/cart/customer attributes. In the admin, the discounts area merges cart + catalog rules into one surface.
Note
A coupon that "doesn't exist" usually means it's inactive, expired, out of usage limit, or scoped to a different segment — the API returns a specific error for each case.
API
See the marketing + catalog-rule mutations/queries in the API reference. Rules are strictly org-isolated.