Comparing marketplace software pricing on the payable event and what sits outside the meter

Marketplace seller software pricing models can be compared only after the meter and included work are fixed. This comparison uses one fictional England seller, one authorised marketplace account and the same product, stock and later order-state exchange. It names no supplier, price or winner.

Research closed on 6 September 2026. Every amount, VAT entry, volume and threshold remains blank until a current exact-offer record exists.

Compare structures, not labels

Structure	Meter to define	Exposure to test	Like-for-like cost entry
Fixed subscription	service, edition, account, billing period and term	limits, excluded functions, renewal and change	subscription plus omitted work and exit
User or seat	eligible user, role, active state and counting date	seasonal access, support users and leavers	charge per defined user plus administration
Product or listing	product, variant, listing state and period	duplicates, suppressed items and archived records	charge per eligible product record
Event or order	precise triggering state and reversal rule	retries, rejected events, cancellation, refund and dispute	charge per auditable eligible event
Revenue-linked	qualifying receipts, currency, deductions and settlement	refunds, disputes, taxes, attribution and timing	charge on the contractually defined base
Project or retainer	deliverable, capacity, acceptance and period	change requests, dependencies and unused capacity	fee plus buyer labour and pass-through cost
Current manual route	task, role, observed time and period	rework, account access and opportunity cost	evidenced internal cash and economic cost

Do not compare a software fee with a managed-service total. One may exclude implementation and operating labour that the other includes. Where a supplier combines meters, model each component and its interaction.

Define the payable event

Order placed, seller acceptance, payment authorisation, capture, fulfilment, settlement, cancellation, return, refund and dispute are separate events. The contract must say which one is billable, when it is counted, how duplicates are removed and whether reversals receive a credit. Supplier terminology needs a mapping to the seller's evidence.

GOV.UK's online-selling page provides the consumer-journey context for ordering, correction and confirmation. It does not define a software charging unit. Commercial counsel must inspect the actual terms.

Normalise the price card

For every model, enter legal supplier, exact edition, UK eligibility, currency, VAT status, unit, billing period, minimum term, committed volume, overage, promotion, pass-through amount, refund treatment, source date and exclusions. Mark the row unknown if any factor prevents a common calculation.

HMRC's VAT-record guidance identifies records for supplies and adjustments. An accountant must decide the particular VAT and accounting treatment; the supplier's display is not the merchant's conclusion.

Add costs that sit outside the meter

Include product-data preparation, interface work, migration, assurance, staff access, reconciliation, support, failed-event handling, correction, security, accessibility and exit. OPSS product-safety guidance shows why product role and traceability work can be separate from software functionality. NCSC supplier-assurance guidance prompts investigation of continuity and secure exit.

Test volume and reversal exposure

Build a buyer-owned volume sheet for products, active users and each billable event. Record the observed source period and exclude staff tests and duplicates. Apply the contract's treatment of rejected updates, cancelled orders, refunds and disputes. A lower unit charge can cost more under a different meter, so show the break point as a blank formula rather than predicting volume.

Run the same low, central and high buyer scenarios for every structure. State which input changed and keep the resulting amount labelled as a scenario, not a quotation.

Use a blank common-period formula:

Comparable cost = fixed charges + metered charges + implementation + internal operation + assurance + exceptions + exit

Run sensitivity only after the buyer has evidenced each input. Consumer, safety, tax, privacy, security, accessibility and exit gates remain outside the cost ranking. If routes cannot be normalised to the same job and period, report them as incomparable rather than selecting a winner.