Discount Safety Rules for Free Shipping: Capping the Subsidy on Small Orders
Bounding a shipping promotion with a spend minimum, a maximum rate covered, and a product-price rule, and why none of them alone guarantees a profitable order.
A shipping promotion can cost more than an order earns when cheap products meet expensive carriers. For a fictional craft retailer, the bound is a $10 maximum shipping rate covered plus a $30 minimum sized so the smallest qualifying cart's gross profit, after fees and packing, still covers the cap. Keeping the subsidy below product value alone does not guarantee a profitable order.
At a glance
- Challenge
- Cheap products shipped by expensive carriers meant the shipping discount sometimes exceeded the order's product value and its gross profit.
- Approach
- Free shipping over a $30 minimum with a $10 maximum rate covered, sized against the smallest qualifying cart's contribution, plus market targeting and profit analytics.
- Discount Prime campaign types used
- Free Shipping
Scenario-based case study: the merchant is fictional and modeled on patterns across Discount Prime stores. Prices, costs and outcome figures are illustrative assumptions for teaching, not measured results from a real store.
Short Answer
A shipping promotion has no natural ceiling: the carrier sets the rate, not the cart. The fix is not to drop the promotion but to bound it. In Discount Prime's Free Shipping campaign that means combining three things: a spend minimum, a maximum shipping rate covered (the subsidy cap), and, for percentage or fixed shipping discounts, the safety rule "Do not allow discount larger than product price".
Two warnings shape everything below:
- Keeping the shipping subsidy at or below the merchandise value does not make an order profitable. Cost of goods, payment fees, and packing still come out of the same order.
- The product-price rule does not shrink the discount to the product value. If the discount would exceed the products' value, that delivery option gets no shipping discount at all.
Recommendation for this scenario: free shipping above a spend minimum, with a subsidy cap set below the gross profit the minimum cart earns, so the worst-case order still covers its own costs.
Fits / Does Not Fit
| Fits when | Does not fit when |
|---|---|
| Many low-value orders, and some ship by expensive carriers or to remote destinations | Shipping cost is flat and low relative to every cart |
| You want to keep a shipping incentive but need a known worst case per order | You already charge customers the full rate and only want a threshold message |
| You know your gross margin and approximate per-order fees | You do not have cost data yet (set up costs first, see the measurement section) |
Scenario and Required Data
Imagine CraftNest Supplies, a fictional Shopify merchant selling crafting materials and replacement parts. All numbers are illustrative assumptions; replace each with your own.
| Decision data | Illustrative value | Where to get yours |
|---|---|---|
| Average product price | $18 | Shopify Analytics |
| Gross margin on products | 50% | Shopify unit cost vs price |
| Payment fees | 2.9% + $0.30 per order | Your payment provider |
| Pick and pack cost | $1.50 per order | Warehouse or 3PL invoice |
| Typical domestic rate | $5 to $9 | Carrier rates by zone |
| Expensive rates | $18 to $40 (express, remote, international) | Carrier rates by zone and service |
The order that started the review
| Line | Amount |
|---|---|
| Product revenue | $7.00 |
| Cost of goods (50%) | -$3.50 |
| Shipping paid by merchant (fully discounted express rate) | -$18.00 |
| Payment fee | -$0.50 |
| Gross result before packing | -$15.00 |
Nothing malfunctioned. The campaign discounted the full rate because no boundary existed.
Sizing the exposure
Illustrative assumptions: 24,000 orders a month, 0.5% of them where the shipping subsidy exceeds the merchandise value, an average shortfall of $9 on those orders.
24,000 × 0.5% = 120 orders a month; 120 × $9 = $1,080 a month, about $13,000 a year.
To size yours, export last quarter's orders with shipping charged by the carrier, product subtotal, and destination, and count orders where shipping cost exceeded merchandise value or gross profit.
The Real Alternatives
| Option | What it bounds | Cost behavior | Fits when |
|---|---|---|---|
| No shipping promotion | Everything | No subsidy; customers pay full rates | Shipping is a small share of order value, or the promotion is not changing behavior |
| Higher spend threshold only | Average economics | Worst case still open: a $60 cart can trigger a $40 express rate | Rates are uniform across destinations |
| Market or country targeting | Destinations you choose in advance | No subsidy outside chosen countries | Expensive destinations are known countries |
| Subsidy cap ("Maximum shipping rate covered") | Merchant's cost per order | Fixed worst case per order | Rates vary widely within a country |
| Product-price safety rule (% or fixed shipping discounts) | Subsidy relative to merchandise value | Removes the discount entirely on options where it would exceed merchandise value | You run a percentage or fixed shipping discount, not free shipping |
Native Shopify free shipping discounts support a minimum purchase amount or quantity, country selection, and excluding shipping rates over a set amount (Shopify Help Center). An excluded rate gets no discount at all, so the customer pays it in full; there is no option to cover part of an expensive rate. If your expensive rates come from a handful of countries or services, the native options may be enough.
What Each Discount Prime Rule Actually Does
| Setting (as labeled in the campaign form) | Available for | Behavior at checkout |
|---|---|---|
| Minimum purchase (amount or quantity) | All shipping discount types | The campaign applies only when the cart reaches the minimum. Measured before other discounts unless the combination toggle is on, in which case it is measured after them. |
| Limit free shipping for expensive shipping rates + Maximum shipping rate covered | Free shipping | Rate at or below the cap: shipping is free. Rate above the cap: the discount equals the cap and the customer pays the difference. |
| Do not allow discount larger than product price | Percentage and fixed shipping discounts | If the discount on a delivery option would exceed the merchandise subtotal, that option gets no discount. For a fixed discount, the configured amount is compared with the subtotal before the rate is considered. |
| Convert discount larger than shipping cost to free shipping | Fixed shipping discounts | If the fixed amount is at or above an option's rate, that option is shown as free shipping. |
| Markets / countries | All | The campaign applies only to the delivery countries you select. |
Limits that matter for this design:
- Only the first delivery group is discounted. In a split shipment, other groups pay their full rate.
- No profit check on shipping. The shipping discount does not read cost or margin. Every safety rule above is a rule about rates and merchandise value, not about profit.
- Remote zones are learned after the fact. If your campaign form shows "Exclude remote zones automatically", know that a country is added to the exclusion list only after a paid order's shipping cost exceeded your cap. The first expensive order from that country is still subsidized up to the cap. Prefer market targeting for destinations you already know are expensive, and test a checkout to an excluded country before relying on it.
- Currency. If you sell in several currencies, test the minimum and the cap in each presentment currency before launch.
Choosing the Numbers
The safe condition is not "subsidy ≤ merchandise value". It is:
Maximum shipping rate covered ≤ contribution of the smallest qualifying cart
where contribution = minimum cart × gross margin − payment fees − pick and pack.
Illustrative assumptions (50% margin, 2.9% + $0.30 fees, $1.50 pick and pack):
| Minimum cart | Gross profit | Fees | Pick and pack | Contribution before shipping | With a $10 cap, worst case |
|---|---|---|---|---|---|
| $20 | $10.00 | $0.88 | $1.50 | $7.62 | -$2.38 |
| $25 | $12.50 | $1.03 | $1.50 | $9.97 | -$0.03 |
| $30 | $15.00 | $1.17 | $1.50 | $12.33 | +$2.33 |
A $20 minimum with a $10 cap already keeps the subsidy below merchandise value on every order, yet the smallest qualifying orders can still lose money. CraftNest's example settles on a $30 minimum and a $10 cap: about two average items, and a worst case that stays positive under these assumptions.
To adapt it: put your own margin, fees, and packing cost into the table, choose the cap from your rate distribution (high enough that most domestic rates are fully covered), then raise the minimum or lower the cap until the worst-case column is at or above zero. Returns and ad costs are not in this table; if they are material for small orders, add them.
Why not just use the product-price rule?
Consider the alternative design: a fixed $10 off shipping with "Convert discount larger than shipping cost to free shipping" and "Do not allow discount larger than product price".
- Merchandise $22, rate $6: free shipping (converted).
- Merchandise $22, rate $18: $10 off, customer pays $8.
- Merchandise $8, any rate: no shipping discount, because the $10 configured amount exceeds the $8 subtotal.
The subsidy never exceeds merchandise value, but a $12 cart can still receive a $10 subsidy on $6 of gross profit. The rule also creates a hidden minimum (merchandise must reach the fixed amount) that shoppers cannot see. A visible spend minimum with a cap does the same job more transparently.
Customer Experience
| Cart A | Cart B | Cart C | |
|---|---|---|---|
| Merchandise | $42 | $34 | $14 |
| Rate chosen | $7 | $18 (express) | $7 |
| Qualifies ($30 minimum)? | ✓Yes | ✓Yes | ✕No |
| Shipping discount | $7 (free) | $10 (cap) | $0 |
| Customer pays for shipping | $0 | $8 | $7 |
- At checkout, Cart B sees the express rate with a $10 discount applied and pays the remaining $8. Standard options at or below $10 show as free.
- The shipping progress bar can tell Cart C how much more is needed to reach the minimum. Whether that nudge works in your store is a hypothesis to measure, not a given.
- Promise the cap honestly in your banner, for example "Free standard shipping over $30", rather than "Free shipping on everything".
Setup and Prerequisites
- Free Shipping / Cart Incentives requires the Prime plan or higher; check the current plan page in the app.
- Shopify unit costs must be filled in for profit analytics to report margin; lines without cost are left out of the profit figures.
- Configure: discount type Free shipping, minimum amount $30, "Limit free shipping for expensive shipping rates" on with "Maximum shipping rate covered" $10, and the delivery countries or markets you serve.
Pre-Launch Tests
| Test input | Expected result |
|---|---|
| Cart $29.99, domestic | No shipping discount; bar shows the remaining amount |
| Cart exactly $30, rate $7 | Shipping free |
| Cart $34, express rate $18 | $10 off; customer pays $8 |
| Cart $34, delivery to a country outside the selected markets | No shipping discount |
| Cart with items from two locations (split delivery) | Only the first delivery group discounted |
| Same cart in a second currency (if used) | Minimum and cap behave as intended |
Measurement and When to Change
- Primary metric: shipping subsidy per order and as a share of revenue, compared with the period before the cap.
- Guardrail: Estimated Profit per order in Discount Prime analytics (after cost of goods, discount, and shipping; payment fees are not included), and the count of orders colored Loss.
- Rule activity: per-order analytics record whether the shipping rate exceeded the cap and by how much. If the cap is hit often on domestic orders, it is too low for your carrier mix; if it is never hit, the minimum may be doing all the work.
- Conversion and AOV: compare with a baseline period of similar season and traffic mix. Without a holdout, treat before/after differences as directional, not causal.
- Stop or adjust if Loss orders persist (check costs and the cap), or if checkout completion falls in segments that now see partial shipping fees.
Takeaway
A shipping subsidy needs a ceiling defined in money, not in hope. Capping what you cover per order and setting the minimum so the smallest qualifying cart can pay for that cap gives a worst case you can state in advance. Bounding the subsidy by merchandise value alone limits the damage but does not guarantee a profitable order.
Frequently asked questions
How do I stop a free shipping promotion from losing money on cheap orders?
Bound both sides: cap the shipping rate you cover per order, and set a minimum cart whose contribution (cart × gross margin, minus payment fees and packing) is at least the cap. With 50% margin, 2.9% + $0.30 fees, and $1.50 packing, a $30 minimum leaves about $12.33 before shipping, so a $10 cap keeps the worst case positive. Use your own numbers.
Does keeping the shipping discount below product value make every order profitable?
No. Cost of goods, payment fees, and packing still come out of the order. A $20 cart at 50% margin earns $10 gross profit; after fees and packing about $7.62 is left, so a $10 shipping subsidy still loses money even though it is below the $20 merchandise value. The safe condition is subsidy at most the contribution of the smallest qualifying cart.
What does Do not allow discount larger than product price do in Discount Prime?
It is available for percentage and fixed shipping discounts. If the discount on a delivery option would exceed the merchandise subtotal, that option gets no shipping discount at all; it does not reduce the discount to the product value. For a fixed discount, the configured amount is compared with the subtotal, so a $10 off shipping offer gives nothing to carts under $10.
What happens when the shipping rate is above the maximum rate covered?
With a free shipping campaign and Limit free shipping for expensive shipping rates turned on, rates at or below the cap ship free, and rates above it receive a discount equal to the cap while the customer pays the difference. Only the first delivery group is discounted, and the shipping discount does not check cost or margin, so the cap is a rate rule, not a profit guarantee.
Can Discount Prime exclude remote zones automatically?
Only reactively, where your campaign form offers the option. A country is added to the exclusion list after a paid order's shipping cost exceeded your maximum rate covered, so the first expensive order from that country is still subsidized up to the cap. For destinations you already know are expensive, restrict the campaign to the markets or countries you want to serve, and test a checkout to an excluded country before relying on it.
Is Shopify's native free shipping discount enough?
Sometimes. Shopify's free shipping discount supports a minimum purchase, country selection, and excluding rates over a set amount; an excluded rate gets no discount, so the customer pays it in full. If you are happy with free or full price, native settings may be enough. Discount Prime's cap instead covers part of an expensive rate. Free Shipping requires the Prime plan or higher.
Go deeper
Run this architecture in your store
Every campaign type in this case study is included in Discount Prime, with profit analytics to verify the margin impact.