Two checkout totals can differ even when the displayed percentages look identical. A supplier needs the order of operations and the basis of any shipping threshold, not a screenshot saying “10% plus20”. This brief keeps arithmetic separate from store eligibility.
Source-bound fact
Shopify applies product reductions before order reductions, with shipping discounts afterwards. Official reference · Checked 17 October 2026.
Filled synthetic acceptance example
Synthetic teaching example, not a client case or a real-store assessment. On narrow screens, scroll to read the complete table.
| Input | Check basis | Expected |
|---|---|---|
| AUD200; product reduction20; order10% | 180 ×0.90 | 162 before tax/shipping |
| Claim free shipping at180 | threshold basis unconfirmed | do not infer from banner |
| Order percentages10% and20% | same eligible subtotal100 | 70, not72 |
Supplier acceptance procedure
- Write amounts in integer cents and identify the discount class for each promotion.
- For each free-shipping offer, record the actual threshold basis and regional restrictions from store settings.
- Compare expected allocations and actual permitted test checkout without paying; repeat below/at/above the threshold.
Interpret the output
The fixture gives162 for the first row. It does not decide whether this merchant can combine those discounts or whether180 qualifies for shipping. Put unexplained allocations on the supplier’s exception list before signing off a promotional landing page.
Explicit limits
No tax, rounding engine, refund policy, app-specific discount implementation or inferred shipping threshold. Eligibility must be independently verified.
Replay the finite teaching model
Save both files in one folder. With Node22 or newer, run the command below. JSON contains explicit inputs and expected results. The script processes synthetic data only, with no network, credentials, payment or API calls. Passing proves the finite model only, not a live integration.
Filled inputs and expectations · Inspectable teaching script
node check.mjs discount-order-calculation-brief.json