--- title: "Usage-Based Billing Software for SaaS & API Products | Fynex" description: "Usage-based billing (metered billing) for SaaS and API products: event metering, seven pricing schemes, spend caps and invoices marked taxable per line." url: "/saas/usage-based-billing" --- Fynex is an AI-native finance operations platform — agentic finance — that automates and orchestrates end-to-end financial workflows for businesses. This page covers “Usage-Based Billing Software for SaaS & API Products” as part of the Fynex finance operation. Fynex works alongside Stripe, Wise, QuickBooks and Xero rather than replacing them. This page is relevant when a business wants invoicing, payments, payouts, reconciliation and cash run as one automated operation rather than staffed across several tools. # Usage-based billing that *counts every event once* Metered billing for SaaS and API products: send usage events, price them seven ways, and the invoice issues itself at period close. *Billing for software.* ## 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 US the leak is usually the pipeline: usage models leak an estimated 4–9% of revenue against 2–4% for flat-rate SaaS (Lago). And the billing layer itself is priced on your revenue — Stripe Billing charges 0.7% of billing volume on top of processing, and Stripe Tax another 0.5% — before a metering vendor is added to feed it. ## How usage-based billing runs on Fynex Meter, price, invoice, collect — one engine, one record. 1. **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](https://docs.fynex.ai/billing-api/v1/docs/usage-ingestion) for redrive. 2. **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](/glossary/minimum-commitment/) and spend caps. Prices are dated versions on the contract ([rate card](/glossary/rate-card/)), so a change never rewrites a billed period. 3. **Preview a price before you ship it** — Run any configuration at up to 100 quantities through the [same engine that bills](https://docs.fynex.ai/billing-api/v1/docs/usage) — graduated against volume, a new cap against the old one — and quote the customer the number the invoice will show. 4. **Invoicing and collection at period close** — The close pass rates the period into invoice lines, numbers the invoice in a [gapless series](/glossary/sequential-invoice-numbering/), marks each line taxable or not, and sends it with a hosted payment link. The payment is traced to the invoice and to any payouts it funds. ## 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 (Stripe Billing / Chargebee + a metering tool) | Fynex | |---|---|---| | Ingest and deduplicate usage events | A metering vendor or an in-house event pipeline feeding the billing tool. | Idempotent event store, late-arrival handling and a dead-letter queue built in. | | Price usage | Tiered and volume prices; hybrid plans (subscription + usage + credits) get awkward. | Seven schemes, included units, minimums and caps on one versioned contract. | | Preview a price change | Test in a sandbox copy of your catalogue. | `prices/evaluate` on the engine that bills, up to 100 quantities per call. | | Cost of the billing layer | 0.7% of billing volume (Stripe Billing) or 0.65–0.9% (Chargebee, Recurly), plus processing. | No separate billing-layer fee: card payments from 1.4% and payouts at 0.5%, billing included. | | From invoice to cash | Billing hands off to a PSP; reconciliation and payouts are separate jobs. | Invoice, payment, split payout and reconciliation on one record. | ## Questions, answered ### What is usage-based billing? [Usage-based billing](/glossary/usage-based-billing/) — also [metered](/glossary/metered-billing/), 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. ### What is the difference between usage-based and metered billing? 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. ### What are the best usage-based billing platforms? 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](/compare/usage-based-billing-platforms/). ### What is the difference between graduated, volume and tiered pricing? 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](/glossary/graduated-vs-volume-pricing/). ### How is sales tax handled on usage-based invoices in the US? Each invoice line is flagged taxable or not and carries the rate you apply, and a tax-exempt buyer's exemption certificate number goes on the document. Since South Dakota v. Wayfair, nexus is economic — commonly $100,000 of sales into a state — and roughly two dozen states tax SaaS in some form, so the decision of where to collect stays with you; Fynex makes every invoice carry what that decision requires. ### Is there an API for usage-based billing? 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](https://docs.fynex.ai/billing-api/v1/docs). Pricing an AI product on top of it: [billing for AI companies](/saas/ai-billing/). ## 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. - **Prepaid credits** — Credit-based pricing: sell credits up front, draw them down on usage, expire and top up — on one ledger. - **Billing for AI companies** — AI billing: price tokens, requests and agent runs so revenue follows inference cost — hybrid plans, credits and caps. - **Usage-Based Billing** — The product page: meter, price, credit and cap — invoiced and collected on their own. ## 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. ## Your money, held under a licence, not a promise We can be your Merchant of Record, with your funds held by a licensed e-money institution. Most tools can't. - **Your funds, safeguarded** — Customer funds are held by Fondy Ltd, an FCA-authorised e-money institution (FRN 900705). - **PCI DSS Level 1** — The highest card-data security standard, on by default. - **Audit logs** — Every movement traceable and ready for review. - **Built-in KYC / KYB** — The switch that turns the business on. ## Meter it once. *Bill it right* --- The AI finance layer for platforms and operators. It runs the money chain and keeps more of it in your business. One platform instead of a dozen. 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