Stacked discounts multiply
Twenty percent followed by fifteen percent is a 32% effective discount, not 35%, because the second reduction applies to the already-discounted price.
Stacked discount, checkout, and margin analysis
Follow every promotion from shelf price to true net cost
Compound three percentage discounts, apply a fixed coupon, add tax, shipping, and membership allocation, subtract rebates and cash back, compare another seller, and inspect the merchant margin.
Plan with context
The advertised percentage is only one step between shelf price and economic cost.
Stacked promotions apply to changing bases, while checkout charges, delayed benefits, reward restrictions, and the seller’s cost determine whether the deal works for either side.
Fixed coupons follow an order
A dollar coupon can produce a different effective percentage depending on whether it is applied before or after other promotions.
Tax uses a legal base
Jurisdictions and promotion types differ on whether coupons, rebates, shipping, and membership charges reduce the taxable amount.
Delayed benefits are not checkout savings
Mail-in rebates and card rewards reduce eventual economic cost but may require claims, eligible payment methods, caps, or statement cycles.
Membership has an allocated cost
Free shipping is not literally free when an annual subscription must be purchased; the relevant share depends on expected use.
Seller margin can disappear
A promotion that attracts volume can still destroy contribution if realized price falls below product and variable costs.
Included
Unit price and quantity, three stacked discounts, fixed coupon, rebate, payment cash back, sales tax, shipping, membership allocation, alternative seller, true net cost, effective discount, incorrect additive comparison, seller cost and margin, target-margin threshold, scenarios, charts, and promotion ledger.
Not included
Coupon exclusions, category caps, reward expirations, financing promotions, tax-specific sourcing, returns after rebates, subscription cancellation, payment fees, inventory costs beyond the entered unit amount, or demand elasticity.
Use it well
Compare true delivered cost across sellers, read promotion order and exclusions, value delayed benefits conservatively, and monitor contribution—not only revenue—when setting discounts.