Contribution Margin After Marketplace Fees, Returns and Import Costs

Calculate marketplace contribution from a closed group of sales, not from the list price or the payout balance. Start with net sales on one declared GST basis. Subtract the marketplace fees actually retained after credits, outbound fulfilment, landed cost attached to units that stayed sold, return handling, the landed cost lost on non-recoverable returns and any other sale-dependent cost included in your definition.

The result is contribution, not net profit. It shows what the SKU and channel produced before fixed overhead, financing, income tax and any other cost you deliberately keep outside the model.

Define contribution before opening the spreadsheet

Contribution is an internal management measure, so write down its boundary. This article uses:

contribution = net sales - sale-dependent costs

contribution margin = contribution / net sales

For this calculation, sale-dependent costs include:

• net marketplace and payment fees after posted credits;
• outbound fulfilment, packaging and seller-funded delivery;
• verified landed product cost;
• return freight, inspection, repacking and disposal incurred by the cohort;
• landed cost lost when a returned unit cannot be resold; and
• directly attributable advertising or another cost included consistently for every compared channel.

State what remains outside the measure. Fixed payroll, software subscriptions, rent, financing, income tax and owner time might matter to the business without belonging in this version of contribution. If those costs are moved in or out between months, the trend stops being comparable.

Do not call the result net profit. A positive contribution says the sales left something to fund fixed costs and profit; it does not prove the business was profitable.

Use one cohort and one tax basis

Choose a cohort that can close cleanly: orders placed in one month, orders dispatched in one week or units from one SKU and marketplace campaign. Allow enough time for refunds, credits and return dispositions to post, then record the cut-off date. Keep late entries in a visible adjustment column rather than silently rewriting an earlier result.

Also choose one GST basis. The ATO explains that GST-registered businesses collect GST on taxable sales and report GST through their activity statement. A management model should not treat GST-inclusive customer receipts as sales revenue while entering claimable costs excluding GST.

For a GST-registered business making taxable sales, an ex-GST view may be useful. Another entity may need a different treatment. Confirm registration, taxable-sale status, credit entitlement and accounting policy with the accountant, then preserve that basis in every period and every channel being compared.

Record these controls beside the calculation:

• cohort start, end and close date;
• marketplace, account, SKU and currency;
• whether sales and each cost field include or exclude GST;
• source-report name and export timestamp;
• landed-cost version and shipment reference; and
• treatment of saleable, repairable and non-recoverable returns.

Build the waterfall from transaction evidence

A settlement statement can show how cash moved without showing the economics of one SKU. Build a source table that can be traced back to orders, units and adjustments.

The landed-cost guide owns the inbound calculation. Bring its verified unit cost into this model rather than substituting the factory invoice price. Freight, duty, clearance and local delivery can materially change the product-cost input before a marketplace sale occurs.

Treat marketplace fees as transactions, not one percentage

Published fee schedules are useful for planning, but the actual-period model needs the seller's own transaction records.

Amazon Australia's seller-fee page says referral fees are calculated on total sales price and vary by category. It also separates selling plans, fulfilment and other possible costs. eBay Australia's selling-fee page describes transaction fees that can include a percentage of the total amount paid and a per-order fee, alongside advertising, return-label and other charges.

This means one marketplace fee % cell can hide several different bases:

• item price, delivery and other amounts included in the fee base;
• a per-order or per-item fixed charge;
• fulfilment based on size, weight or service;
• advertising charged per click or sale;
• storage, return label, dispute or performance-related charges; and
• credits that post only when policy conditions are met.

Fee reversals deserve their own field. eBay's fee-credit guidance shows that eligible credits depend on the refund path and fee type, and that some fixed or other fees may not be credited. Do not reverse the original fee in the spreadsheet merely because customer revenue was refunded. Record the credit when it appears, or mark it pending.

Use the published fee page to check whether the transaction report looks plausible. Use the transaction report as the evidence for the closed cohort.

Model returns without double counting

A return can affect revenue, fees, fulfilment, inventory and handling at different times. Process each returned unit through one disposition branch.

Saleable return

Remove the refunded sale from net sales. Record any retained fee, outbound fulfilment, return freight, inspection and repacking. Return the unit to saleable inventory in the operational record. Do not also treat its full landed cost as permanently lost.

Repairable or discounted return

Record the refund or discount, retained charges and the actual repair, repack or markdown effect. Keep the unit's inventory treatment consistent with the entity's accounting policy. Do not use an invented standard return cost if the disposition evidence is available.

Non-recoverable return

Remove the refunded sale and record the retained transaction and handling costs. Include the landed cost that is no longer recoverable from that unit in this operational cohort, subject to the entity's inventory and accounting treatment.

The legal reason for a remedy matters. The ACCC states that businesses must provide remedies when consumer guarantees are not met, with the available remedy depending on the problem. This article does not decide a specific consumer dispute. It uses completed refund and disposition records, not a legal assumption, to measure cost.

The ecommerce return-reason quality loop takes the next step: it separates suspected causes from verified causes and routes recurring signals into product controls. The margin model shows the commercial effect; it does not diagnose the defect by itself.

Worked example: 100 marketplace orders

Every figure below is fictional. The example assumes one SKU, one Australian marketplace cohort and a consistent GST-exclusive management-cost basis. Customer receipts and refunds are shown GST-inclusive, then converted to the assumed ex-GST sales basis by dividing by 1.10. This is a teaching assumption, not tax advice.

The cohort contains 100 orders at AUD66 each including GST. Five units are fully refunded. Three returned units pass inspection and return to saleable inventory; two are non-recoverable. The verified landed cost is AUD18 per unit.

The three saleable returned units are not assigned another AUD54 of lost landed cost. They are back in saleable inventory in this operational model. Their original outbound fulfilment and their return processing remain costs of the cohort.

The result is AUD18.89 per original order or about AUD19.88 per net sold unit. Those denominators answer different questions, so label them. Neither number is net profit.

Stress-test the return and fee assumptions

A point estimate is fragile when return outcomes or fee credits are incomplete. Run at least one downside using the same formula.

This fictional downside changes five inputs: ten orders are refunded, five returned units are non-recoverable, net marketplace fees are AUD760, return freight and processing are AUD60, and 90 units remain sold. Fulfilment, advertising and landed unit cost stay unchanged.

The downside margin falls by 4.0 percentage points. That difference does not prove future returns will rise. It shows how much decision headroom remains if the stated assumptions occur.

Do not apply one return-rate benchmark to every SKU. Use observed rates by product, channel, reason and disposition, then show the sample size and close date. A product with a low return count can still have severe cost if the returned units are bulky, unsafe or non-recoverable.

Reconcile the result to source reports

Close the cohort with a short control sequence:

1. Tie order count and gross receipts to the marketplace order report.
2. Tie refunds and partial refunds to transaction entries.
3. Tie fee debits and credits to the financial statement or settlement export.
4. Tie fulfilment, return-label and other service charges to their own transaction types.
5. Tie units that stayed sold to the inventory movement record.
6. Tie each return to a disposition and any saleable stock movement.
7. Tie landed unit cost to the correct shipment and cost version.
8. Record pending credits, late invoices and unresolved dispositions separately.

The reconciliation should explain the difference between the marketplace payout and contribution. Payout is a cash settlement after selected debits and credits. Contribution also needs landed product cost and any relevant costs held outside the marketplace account.

If the transaction exports cannot be tied to the cohort, mark the result provisional. A polished percentage is not useful when the underlying orders, fees and units do not reconcile.

Turn the calculation into a product decision

Compare the SKU across time, channel and scenario only after the definition is stable.

• If fee leakage is driving the change, inspect category, plan, fulfilment tier, listing settings and current marketplace terms.
• If outbound fulfilment dominates, test packaging dimensions, service level and seller-funded delivery rules.
• If non-recoverable returns dominate, follow the cost-of-poor-quality framework into prevention, inspection and supplier recovery.
• If landed product cost changed, reopen the shipment allocation and supplier/FX variance rather than blaming the sales channel.
• If contribution is positive but too thin for fixed costs and risk, use the import-order break-even model with the same contribution basis.

Set decision thresholds before seeing the result. Examples include a minimum contribution dollars per unit, a minimum contribution margin, a maximum downside loss, or a review trigger when return cost exceeds a declared share of net sales. These are company decisions, not universal benchmarks.

What this model does not tell you

Contribution does not determine financial-statement profit, taxable income, inventory value, GST liability or cash timing. It also does not prove that an advertising campaign caused the orders attributed to it, or that a return reason identifies the root cause.

Use a qualified accountant for GST, inventory, expense recognition and statutory reporting. Use current marketplace account data for fee treatment. Use product and quality evidence for corrective action. The calculation is valuable because it keeps those inputs visible rather than collapsing them into a single payout or markup percentage.

Sources

• Amazon Australia — Seller Fees
• eBay Australia — Selling Fees
• eBay Australia — Fee Credits
• Australian Taxation Office — Accounting for GST in Your Business
• Australian Taxation Office — GSTR 2000/19: Making Adjustments Under Division 19
• Australian Competition and Consumer Commission — Repair, Replace, Refund, Cancel
• Australian Accounting Standards Board — AASB 102 Inventories