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Northwind AI Ltd · SeptemberInvoice preview
API calls2.4M · 1M included
£560
Platform feemonthly
£500
Spend caphard · 42% used
On
Prepaid creditapplied at issue
−£200
The problem
A flat plan quietly loses money on the customers who use you most
Every request your product serves costs you something — inference, compute, a third-party API. A flat plan is priced on the average user, so your heaviest customers turn into your least profitable ones, and you find out when the cloud bill lands. Moving to usage fixes the maths and breaks the billing: events have to be counted once, priced, and turned into an invoice nobody disputes.
In a 2026 m3ter and PwC survey of 350 UK software executives, 44% struggled to capture usage data, revenue leakage ran at 4–7% of ARR, and 87% of billing systems weren't connected to the general ledger. The margin problem and the invoice problem are the same problem.
Heavy users · this monthFlat plan
Top 5% of customersshare of usage
61%
Their planflat, monthly
£200
Cost to serveinference + compute
£1,840
How it works
From the first request to the payment booked
Three steps from setup to settled — then it runs itself.
1
Meter what costs you money
Name a metric — API calls, tokens, seats, gigabytes — and send events by API, batch or CSV. A duplicate is dropped on its key, and a refused event waits in a queue to retry instead of vanishing from the invoice.
2
Price it the way you sell
Per unit, graduated, volume, tiered, package, percentage or per seat, with included units, a minimum and a spend cap. Try any price at any volume on the same engine that bills, before a customer ever sees it.
3
The invoice issues itself
At period close the usage is rated, the VAT invoice is numbered and sent with a payment link, and the payment is matched back to it — VAT on every line, the total in sterling, prepaid credit applied after VAT.
What comes off your plate
Usage that turns into revenue you can see
The four things a usage model breaks, and what happens to each.
Metering
Every event reaches the invoice, once
Each event carries its own key, so a retry never bills twice and a late event lands in the right period. Anything refused — an unknown metric, an unmatched contract — is held with its reason for you to retry or discard.
Events · last hour
Accepted
184,220
Duplicates droppedsame key
312
Held for retryunknown metric
4
Seven pricing schemes
A new price without a new release
A price is a dated version on the customer's contract. Change a tier from the first of next month and last month's invoices keep the price they were billed on — no migration, no ticket.
api_calls · price versions
v2 · from 1 Octgraduated
£0.0004 → £0.0002
v1 · Jul–Sepper unit
£0.0004
Includedper month
1,000,000
Prepaid credits
Cash in before the cost goes out
Sell credits up front and draw them down as customers use you. Top-ups, expiry and eight credit types — purchased, promotional, AI-token and more — sit on one ledger, and the unused balance exports as the liability your accountant asks for at year end.
Credit ledger · Northwind AI
Top-uppurchased
£5,000
Drawn this monthapplied at issue
−£1,240
Balanceexpires 31 Mar
£3,760
Alerts & caps
No bill shock, for them or for you
Set a threshold and a cap per metric. Your customer hears at 80% instead of on the invoice, a hard cap stops usage where you agreed it would, and a spend cap stops the bill even when usage runs on.
api_calls · capHard cap
Used
4.1M
Alert sentat 80%
Yes
Show, don't tell
One customer's month, priced before it's billed
A platform fee, 2.4 million API calls against a million included, VAT, and a prepaid credit applied after it — rated on the engine that bills, so the preview and the invoice agree to the penny.
Platform fee + API calls£1,060
VAT at 20%£212
Prepaid credit applied−£200
Due · paid on the link£1,072
The intelligence layer
What it catches before the usage invoice goes out
Fynex reads usage as it arrives and prices it as it goes, so a customer about to hit their cap, an event nobody can bill and a plan that costs more to serve than it earns surface in the month — not on the invoice, and not in the cloud bill.
Warns a customer before they cross their cap, not after
Holds events it can't bill — unknown metric, unmatched contract — for retry
Shows which customers cost more to serve than they pay
Flags the plan a heavy-usage cohort has outgrown
Recommends the price change, and never applies it without your approval
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
!Count usage accurately
✕Other platformsBuild an event pipeline, or add a metering vendor on top.
✓FynexMetering built in: one key per event, late events, a retry queue.
!Change a price
✕Other platformsA new price object, a migration and a release.
✓FynexA dated price version on the contract; history untouched.
!Sell prepaid credits
✕Other platformsA wallet you build and reconcile yourself.
✓FynexA credit ledger with top-ups, expiry and a liability export.
!Pay for the billing layer
✕Other platforms0.7% of billing volume (Stripe Billing), on top of processing.
✓FynexNo billing-layer fee on top: the card rate on what you collect, from 1.4%, covers it.
!Get paid, then pay out
✕Other platformsBilling hands off to a processor; payouts are another vendor.
✓FynexInvoice, payment, split payout and reconciliation on one record.
Everything you get
The rest of the job, also handled
Beyond the headline job, every account gets the whole platform behind it.
Per-seat pricing
Seats rated from their history, prorated to the day.
Test clock
Run a year of renewals in the sandbox in a minute.
Usage by CSV or webhook
Send events from a warehouse export or a webhook — no code.
Every invoice, credit and subscription state as an event.
Invoice to payout trail
Each invoice traced to the payment and the payouts it funded.
One platform, not a dozen
Your product, your books and your bank, kept in agreement
Usage from your product or your warehouse, invoices out, payments matched back into your accounting system.
100+ integrations
Accounting stack
13
Every payment, fee and payout lands in your ledger, coded and reconciled — nobody re-keys it.
QuickBooks
QuickBooks
Xero
Xero
FreshBooks
FreshBooks
Sage
Sage
NetSuite
NetSuite
Wave
Wave
Banks & business accounts
18
We read your balances and pay out of whichever account is cheapest — no bank portals, no copy-paste.
Revolut
Revolut
Wise
Wise
Mercury
Mercury
Brex
Brex
Airwallex
Airwallex
Ramp
Ramp
Project & time tracking
9
Hours, retainers and delivery status — so a project's real margin shows up without a spreadsheet.
monday.com
monday.com
Asana
Asana
Jira
Jira
ClickUp
ClickUp
Trello
Trello
Linear
Linear
Site & app builders
9
Whatever you built the business on — payments, invoicing and payouts wire into it without a dev project.
Webflow
Webflow
Framer
Framer
Lovable
Lovable
Bubble
Bubble
Softr
Softr
Glide
Glide
CRM & sales
7
The deal, the customer and the terms — pulled in so invoicing starts itself.
HubSpot
HubSpot
Salesforce
Salesforce
Pipedrive
Pipedrive
Zoho CRM
Zoho CRM
Close
Close
Copper
Copper
Payment acceptance
10
Keep the checkout you already run. We take it from the moment the money lands.
Stripe
Stripe
PayPal
PayPal
Adyen
Adyen
Square
Square
Braintree
Braintree
Checkout.com
Checkout.com
Your customers pay however they already pay — Visa, Mastercard, American Express, Apple Pay, Google Pay, Faster Payments, bank transfer and open banking — through the provider you run today or through us.
Find what you're leaking, for free
Send us your setup. We run a free diagnostic and show you what your payment stack costs you today.
One recent diagnostic found £2M in hidden fees across 10 processors for a proptech client.
Usage-based billing charges customers for what they actually consume — API calls, tokens, compute, seats or transactions — instead of one flat fee. Fynex meters the usage, prices it on your terms, issues the invoice at period close and matches the payment back to it, so the revenue follows the cost of serving each customer. For AI products specifically, see billing for AI companies.
You register a metric (sum, count, unique count, max, min or last value) and send events by API, in batches of up to 500, by CSV or by webhook. Each event carries an idempotency key, so retries never bill twice; refused events are held with a reason for you to retry or discard. The usage guide documents every field.
Seven: per unit, graduated, volume, tiered, package, percentage and per seat — each with optional included units, a minimum commitment and a spend cap. Prices are dated versions on the customer's contract, and any configuration can be previewed at any volume on the same engine that bills.
A customer buys prepaid credit up front; it is drawn down against their invoices as they're issued. Credit is applied after VAT — it pays the invoice rather than discounting it — so the VAT on the invoice stays correct. Eight credit types (purchased, promotional, AI-token, enterprise and more) share one ledger with expiry, and the unused balance exports as a liability for your accounts. More in prepaid credits billing.
Yes. Each invoice carries HMRC's full VAT invoice fields — a gapless sequential number, time of supply, both parties, VAT category and rate per line — with the VAT total shown in sterling whatever currency you bill in. B2B customers in the EU get reverse-charge wording enforced, and simplified invoices up to £250 are supported.
Stripe Billing, Orb and Metronome meter and invoice; the payment, the payouts and the reconciliation live with a processor and other vendors — and Metronome is now part of Stripe, Orb part of Adyen. Fynex meters, invoices, collects, splits and reconciles on one record, beside the processor you keep. The full comparison is in the best usage-based billing platforms.
Yes — the Billing API covers metrics, events, prices, contracts, subscriptions, invoices and credits, with a sandbox and a test clock. Most teams configure prices from the dashboard and send events from their product; the API is there when you want billing driven by your own system.
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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