A promotion is the fastest way to lift average order value and the fastest way to give away margin for nothing. The difference between those two outcomes is not creative, it is in how the rules are configured: what combines with what, whether there is a ceiling, and whether the promotion switches itself off when it ends.
Below: the mechanics — which rule types exist, what happens when several of them claim the same cart, and which settings protect the money. This is the part of the marketing toolkit that pays back fastest, and costs the most when it is wrong.
A rule is a condition plus a reward
Any promotion decomposes into two parts. The condition is what triggers it: item quantity, cart total, membership of a category or brand. The reward is what the buyer gets: a percentage discount, a fixed sum, a gift product.
| Type | Condition | Reward |
|---|---|---|
| Gift for quantity | bought N items | a product as a gift |
| Cart discount | total over X | a percentage or a fixed sum |
| BOGO | bought one | the second free or cheaper |
| Tiers | the larger the total, the larger the discount | a rising percentage |
| Combo | a set of specific items | a discount on the set |
The first two work for free in CommerCentr — enough to run a sale or a «gift over a threshold» campaign. The remaining types, along with stacking control, are in the paid extension.
The real question: what happens when there are several rules
This is where the most expensive mistake hides. A buyer assembles a cart and three promotions claim it at once: a category discount, «10% off over 2,000» and a coupon from an email. What should they pay?
The free tier answers simply and safely: only the single best rule for the buyer applies. Nothing adds up. That is a deliberate boundary rather than a simplification: without stacking control three rules compound, and an item priced at 1,000 ships for 400.
The paid tier is precisely about governing that:
Rule-plus-rule stacking. Allow or forbid two promotions combining. Forbidden by default, and worth enabling only where you have worked the total out on paper.
Coupon-plus-rule stacking. A separate question, because the buyer brings a coupon from outside — from an email, from an influencer. Shops often want the promotion to apply but not a coupon on top of it.
Apply order. Once stacking is allowed, order changes the sum: a percentage off a reduced base is not the same as off the original. The order is stated explicitly rather than left to chance.
Discount ceiling. An upper limit on the total discount for a cart. This is insurance against the case you did not foresee: however many rules coincide, the shop gives away no more than the ceiling.
The validity window: a promotion that ends by itself
The second most expensive mistake is a promotion nobody switched off. «40% off today only» on the fourth day does not merely look silly: a buyer who paid full price yesterday sees a promise they did not get.
So a rule has a validity window — a start and an end. Empty fields mean «no limit», so standing mechanics like «a gift with every order» work without dates. But anything called a promotion must have an end date.
A practical rule: if you cannot name the finish date, it is not a promotion, it is a new price. And then it belongs in the price, not in a promo rule — otherwise in six months nobody will remember why the item sells cheaper.
Limits: how many times
The third protective block is usage limits. Without them one promotion can eat more than planned, and it will do so quickly.
Per-order limit — how many times the rule fires within one cart. Without it, «every third one free» on an order of thirty items gives away ten.
Per-customer limit — how many times one person can use the promotion. It guards against the scenario where someone finds an attractive offer and buys out the stock with it.
Total limit — how many times the promotion fires at all. This is how to make an honest limited offer: not «hurry, few left» on an invented counter, but a real boundary after which the promotion simply ends.
Categories and subcategories
A small thing that changes reach by an order of magnitude. A category rule can apply to that category alone or to the whole subtree. «Discount on footwear» should normally cover men's, women's and children's — that is, include subcategories. «Discount on the clearance category», by contrast, should not.
In CommerCentr this is a checkbox on the rule, and it is on by default: the subtree is included. Before launching, check it deliberately for every rule that targets a category — this is the easiest place to miss by a factor of ten.
A coupon and a promotion are different things
They are often confused, and they behave differently — and the nastiest surprises appear exactly where they meet.
A promotion applies by itself. The buyer does nothing: the condition matched, the discount applied. Everyone who qualifies sees it, and it works across all your traffic.
A coupon is brought by the buyer. It is a targeted instrument: a code from an email, from an influencer, on a gift card. It has its own limits and expiry, and it lives in its own system rather than in promo rules.
The question to answer in advance is whether they work together. Someone arrives from an email with 10% off, and the item is already on a 30% promotion. If coupon-plus-rule stacking is allowed, the result is roughly 37% or 40%, depending on order. If forbidden, one of them applies.
Both answers are legitimate, but they have to be deliberate. The worst case is not knowing which one you have enabled; then you find out from the first order where the discount turns out larger than the margin.
A practical approach: make coupons for the people a promotion does not cover — bringing back a lapsed customer, compensating an inconvenience, thanking someone for a review. Stacking then becomes a rare case rather than daily arithmetic.
Where shops lose money
Three scenarios, each of which turns up in real configurations.
Stacking with no ceiling. Stacking was allowed «to be generous», and the worst case was never calculated. When three rules coincide the discount exceeds the margin, and every such sale is a loss.
A discount on an item already at its floor price. A category rule does not distinguish which items are already marked down. If the category holds items near cost, they go below it.
A promotion with no per-customer limit. One person places twenty orders in a row before anyone notices. Formally it is not a violation — you configured it that way.
What all three share: the mistake is invisible at the time and shows up at the end-of-month reconciliation, when the goods have already shipped.
The order to configure things, if this is your first time
- Calculate the worst case on paper — not the average, the worst: every rule that could theoretically coincide, coinciding.
- Set the discount ceiling before you create the first rule. It is insurance against what you did not foresee.
- Leave stacking off until there is a specific reason to turn it on.
- Give an end date to every rule you call a promotion.
- Check the category subtree — do you really mean to cover all of it.
- Run a test order with the most «advantageous» cart you can assemble and look at the total.
What this does not do
Promo rules do not manage prices. The base price and any markdown live on the product card; a promo rule only adds a discount on top. If you simply need to sell cheaper, that is a price, not a promotion.
They also do not make an offer attractive. A BOGO mechanic on a product nobody wants returns zero. A promotion amplifies demand that already exists; it does not create it from nothing.
And they do not replace analytics. The system will calculate the discount, but it will not tell you whether the promotion made money. That is worked out by hand: revenue minus cost minus the discount given, compared against a period without the promotion.
Summary
A promotion consists of three things, and only the first is creative: the mechanic, stacking control and an end date. The second and third are what separate a profitable promotion from an expensive one.
Two of the most common mechanics work for free in CommerCentr — a gift for quantity and a cart discount, with «best rule only» stacking. That covers most sales. The Promo extension is for when several promotions run at once and the question of what combines with what appears — that is where the ceiling, the limits and the apply order live.
Reduced to one rule: work out what you would give away in the worst case first, and only then switch it on. A promotion whose upper bound you do not know will eventually show it to you.
See also product sections on the storefront — a promotion also has to be visible in the catalogue — and catalogue SEO, so promotional pages do not fall outside the index.