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The problem
Usage-based pricing is easy to announce and hard to bill
Usage-based billing (also called metered or consumption billing) charges each customer for what they used in the period — API calls, tokens, seats, GB, transactions. Most SaaS companies have adopted it or are adopting it; Metronome's 2025 survey put the figure at 85% of 100 companies. The hard part is the pipeline behind the invoice: ingest events, drop duplicates, place late events in the right period, aggregate, rate against the price, and issue a document the customer can check line by line. Every step that drops an event is revenue that never reaches the invoice.
In the UK the leak is measured: a 2026 m3ter/PwC survey of 350 UK software executives found 44% struggle to capture usage data, 4–7% of ARR leaks, and 87% of billing systems aren't integrated with the ERP or general ledger. Half of them changed pricing two or more times in a year — each change another migration in a billing tool that versions badly.
Usage pipeline · SeptemberMetered
Events received
18.4M
Duplicates droppedidempotency key
41,200
Late eventsplaced in August
3,118
Refused · heldunknown metric
12
What Fynex runs
How usage-based billing runs on Fynex
Meter, price, invoice, collect — one engine, one record.
Unified metering
Metering: events in by API, batch, CSV or webhook
Register a metric with an aggregation — sum, count, unique count, max, min or last — and send events one at a time, in batches of 500, as a CSV or through a signed inbound webhook. Each event carries an idempotency key; refused events wait in a dead-letter queue for redrive.
Pricing engine
Rating: seven pricing schemes on one contract
Per unit, graduated, volume, tiered (stairstep), package, percentage in basis points and per seat prorated to the day — with included units and rollover, minimum commitments and spend caps. Prices are dated versions on the contract (rate card), so a change never rewrites a billed period.
prices/evaluate
Preview a price before you ship it
Run any configuration at up to 100 quantities through the same engine that bills — graduated against volume, a new cap against the old one — and quote the customer the number the invoice will show.
Invoice composer
Invoicing and collection at period close
The close pass rates the period into VAT invoice lines, numbers the invoice in a gapless series, shows the VAT total in sterling, and sends it with a hosted payment link. The payment is traced to the invoice and to any payouts it funds.
Usage invoice · Oct
api_callsgraduated
£560
seatsper seat · prorated
£270
Status
Sent · link
How we compare
The same job, with the leaks closed
Point tools solve part of it. Fynex runs the whole thing on one platform.
The problem
Other platforms
Recommended
!Ingest and deduplicate usage events
✕Other platformsA metering vendor or an in-house event pipeline feeding the billing tool.
✓FynexIdempotent event store, late-arrival handling and a dead-letter queue built in.
!Price usage
✕Other platformsTiered and volume prices; hybrid plans (subscription + usage + credits) get awkward.
✓FynexSeven schemes, included units, minimums and caps on one versioned contract.
!Preview a price change
✕Other platformsTest in a sandbox copy of your catalogue.
✓Fynex`prices/evaluate` on the engine that bills, up to 100 quantities per call.
!Cost of the billing layer
✕Other platforms0.7% of billing volume (Stripe Billing) or 0.65–0.9% (Chargebee, Recurly), plus processing.
✓FynexNo separate billing-layer fee: card payments from 1.4% and payouts at 0.5%, billing included.
!From invoice to cash
✕Other platformsBilling hands off to a PSP; reconciliation and payouts are separate jobs.
✓FynexInvoice, payment, split payout and reconciliation on one record.
FAQ
Questions, answered
Usage-based billing — also metered, consumption or pay-as-you-go billing — charges a customer for what they consumed in a billing period: API calls, tokens, compute hours, seats, storage or transaction value. A usage-based billing platform ingests usage events, aggregates them per customer, rates them against a price and issues the invoice. Fynex does all four and collects the payment.
In practice they are the same thing. "Metered billing" describes the mechanism — a meter counts units — and "usage-based billing" describes the pricing model built on it. Hybrid pricing combines a recurring platform fee or seat fee with metered usage above an included allowance, which is the most common shape for SaaS and AI products in 2026.
Stripe Billing, Fynex, Orb, Metronome, Chargebee, m3ter and Lago are the names most teams shortlist. Stripe Billing (now with Metronome) suits companies already on Stripe; Fynex runs metering, invoicing, collection and payouts on one record; Orb (Adyen) and Metronome (Stripe) target high-volume AI and infrastructure; Chargebee suits subscription-first SaaS; m3ter (being acquired by Salesforce) feeds CRM and ERP; Lago is open source and self-hosted. Full breakdown: the best usage-based billing platforms.
With graduated pricing each band charges its own rate for the units inside it, like income tax. With volume pricing the band the total lands in prices every unit at that band's rate. Tiered (stairstep) pricing charges a flat amount for the band the total lands in. Same bands, same quantity — three different invoices, which is why Fynex previews all of them on the billing engine. Worked example: graduated vs volume pricing.
Yes. Fynex invoices carry the full VAT invoice fields in HMRC Notice 700/21 — a gapless sequential number, time of supply, supplier and customer details, VAT category and rate per line, and the VAT total in sterling even when you bill in dollars or euros. Reverse-charge wording is enforced for B2B customers in the EU, and simplified invoices up to £250 are supported.
Yes. The Fynex Billing API exposes metrics, usage events (single, batch, CSV), dead letters, per-contract prices, `prices/evaluate`, contracts, subscriptions, invoices and credits, with a sandbox and a test clock. Reference: docs.fynex.ai/billing-api/v1/docs. Pricing an AI product on top of it: billing for AI companies.
Keep building
The rest of the billing layer
Every guide below runs on the same billing engine and the same money. Start with one, or run the whole stack.
We can be your Merchant of Record and hold the funds. Most tools can't, because they don't hold the licence.
FCA-authorised EMI
An e-money institution via Fondy. We can hold and move your funds.
Licence
E-money institution
FCA
Client funds
Safeguarded
PCI DSS Level 1
The highest card-data security standard, on by default.
Card data
PCI DSS
Level 1
Encryption
On by default
Audit logs
Every movement traceable and ready for review.
Activity
Payout · £23,84714:02:11
Logged
Split · ORD-2024-00114:02:09
Logged
Built-in KYC / KYB
The switch that turns the business on.
Verification
KYB · Northwind Labs Ltd
Approved
KYC · J. Whitfield
Approved
We do Fridays so you don't have to.Payouts at midnight. You, asleep.Invoices that chase themselves. Ruthlessly.We carry the chargebacks. You carry on.We do Fridays so you don't have to.Payouts at midnight. You, asleep.Invoices that chase themselves. Ruthlessly.We carry the chargebacks. You carry on.We do Fridays so you don't have to.Payouts at midnight. You, asleep.Invoices that chase themselves. Ruthlessly.We carry the chargebacks. You carry on.
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