Allow
The stacked discount still clears your encoded margin floor — the codes apply, recorded as a signed pass.
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Decionis for Commerce
Answer · Stop coupon stacking at checkout
How do I stop coupon and discount stacking at checkout?
To stop coupon and discount stacking at checkout, enforce a hard margin floor at the moment the order is priced — not a rule that merely limits which codes combine. Decionis computes cost-basis-aware net margin inline at checkout and blocks stacked or unauthorized discounts before the checkout token is issued, in under 120ms of decision compute, sealing each decision into an Ed25519-signed Decision Dossier. It is deterministic — a fixed threshold against your verified cost basis, not an AI model — and it installs read-only in Shadow Mode first, so you see every stack it would have blocked before it enforces anything.
Why native Shopify discount rules aren't enough
Shopify's discount combinations and Functions can decide which codes combine. They can't compute the net margin those stacked codes actually leave, or fail closed with proof.
| Dimension | Native Shopify discount rules / Functions | Decionis |
|---|---|---|
| What it evaluates | Which codes may combine and how many apply per order. | The resulting net margin after every stacked discount, against your verified cost basis. |
| Failure mode | Two individually valid codes can still stack an order below cost. | Fails closed — the checkout is held before the token is issued when the floor is breached. |
| Proof of the decision | No signed record of why an order was allowed or blocked. | An Ed25519-signed Decision Dossier with the margin math and policy version. |
| Determinism | Rule behavior varies as promotions and app logic change. | Deterministic — same cart and codes, same verdict, every time. No AI, no model drift. |
The verdicts
One certified outcome per checkout — deterministic from the same inputs every time.
Hold (block)
The combined discount would drop net margin below the floor — the stack is suppressed before the checkout token is issued.
Review
Item cost is missing in Shopify, so margin can't be computed — flagged for cost entry rather than guessed. Never a fabricated cost.
What the Decision Dossier records
Every held or allowed checkout produces a signed, exportable receipt — the fields finance needs for month-end reconciliation and dispute defense.
| Cart total | Pre-discount order value evaluated at checkout |
| Codes applied | Each coupon or automatic discount the cart attempted to stack |
| Discount amount | Total combined order-level discount from the stacked codes |
| Estimated cost basis | Sum of real unit costs (Shopify InventoryItem.unitCost), never assumed |
| Net margin % | (revenue − discount − cost) / (revenue − discount) — the deterministic verdict input |
| Margin at risk (USD) | Dollars the stacked order would have leaked below your floor, computed for held orders |
| Policy version + floor | The encoded margin-floor policy and rule digest that governed the decision |
| Verdict | Allow, hold, or review — one certified outcome at the checkout boundary |
| Signature + hash | Ed25519 signature over the canonical SHA-256 of the dossier (when the prod key is provisioned) |
It governs the floor, never the strategy
- Which promotions or codes you should run — that is your merchandising decision.
- Whether a coupon campaign is a good idea — only whether a stacked order clears the encoded floor.
- Fraud or coupon-abuse detection — that is a separate control layer.
- An end-to-end checkout latency claim — only the deterministic policy evaluation is benchmarked at <120ms; Shopify's Function runtime and network are outside Decionis's control.
Frequently asked questions
Stopping coupon stacking at checkout, and how the margin floor decides.
How do I stop coupon and discount stacking at checkout?
Enforce a hard margin floor at the moment the order is priced, not just a rule about which codes may combine. Decionis computes cost-basis-aware net margin inline at checkout and blocks stacked or unauthorized discounts before the checkout token is issued, in under 120ms of decision compute. The decision is deterministic — a fixed threshold against your verified cost basis, not an AI model — and each block is sealed into an Ed25519-signed Decision Dossier.
Can't I just use Shopify's native discount combinations or Functions?
Native discount rules and Shopify Functions can control which codes combine and cap how many apply, but they don't compute net margin against a verified cost basis, and they don't fail closed with cryptographic proof. Two individually valid codes can still stack an order below cost. Decionis governs the outcome — the actual net margin after every stacked discount — and holds the checkout when it breaches your encoded floor.
Will Decionis block legitimate discounts my team intended?
No. Decionis only holds orders where the combined discount pushes net margin below the floor you encoded. Stacks that clear the floor apply normally and are recorded as signed passes. It governs the margin floor, never which promotions you choose to run.
Does it use AI or an LLM to make the decision?
No. The margin gate is deterministic — a fixed mathematical threshold evaluated against your real cost basis. The same cart and the same codes always produce the same verdict, with no model drift. Decionis installs read-only in Shadow Mode first, so you see every stack it would have blocked before it enforces anything.
Self-serve · read-only first
Watch it block a below-floor stack — before you enforce anything.
Run a stacked-discount cart through the sandbox, read the signed Decision Dossier with the margin math, then enable enforcement from the quickstart when the verdict is right.