How are coupons and loyalty points applied and totals recomputed at checkout?

At checkout a customer can apply a coupon and/or redeem loyalty points. The system validates each, applies the discount or point redemption, and recomputes the totals (and any interaction with fees). Loyalty points convert to currency at a configurable value, and coupons reduce the total per their type and eligibility. Because totals are recomputed on application, the customer…

At checkout a customer can apply a coupon and/or redeem loyalty points. The system validates each, applies the discount or point redemption, and recomputes the totals (and any interaction with fees). Loyalty points convert to currency at a configurable value, and coupons reduce the total per their type and eligibility. Because totals are recomputed on application, the customer always sees the accurate final amount, and invalid or ineligible incentives are rejected with a clear reason rather than silently mis-applied.