Can I charge per request rather than per month?

Yes. Usage-based and pay-as-you-go pricing are supported, and you can add one-off charges to a live subscription for overages rather than holding them until the next renewal.

How do I keep API keys in step with billing?

Drive them from webhooks. Activate on payment_success, and throttle or revoke on the subscription cancellation and failed-payment events. Your issuer becomes a consumer of billing state rather than a second source of truth.

Do business customers get invoices?

Yes, when they enter their B2B details including a tax ID at checkout. Turn the billing step on in the dashboard so those fields appear, and the invoice is emailed to them automatically.

Can I preview what a plan change will cost?

Yes. The API can preview an upcoming renewal, which is what you show a developer before they confirm an upgrade so the prorated amount is not a surprise.

Is there tooling beyond the REST API?

A JavaScript SDK, an npm package, a CLI, and an MCP server with documented Cursor, Claude and VS Code integration. Webhooks have a synthetic test-event endpoint for local development.

SaaS · API products

Billing for something bought by the request.

Selling an API means the invoice is a function of what somebody's cron job did last month, and the key has to stop working the moment the card does. Usage charges, plan tiers and webhook-driven entitlements are how that gets wired.

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No upfront costs. No credit card required.

Already selling with Fungies

0
core API resources you can drive it all from: 0+
payment methods for your customers: 0% + 50¢
the only charge: $0
monthly fee on a quiet month

The shape of an API business

001

Usage

Tiers plus what went over them

A plan with an included allowance, then pay-as-you-go beyond it. One-off charges can be applied to a live subscription, so an overage does not have to wait for the next billing date.

002

Entitlements

Keys follow the subscription

Your issuer listens to the payment and subscription webhooks and switches the key on and off. A failed renewal degrades access on its own instead of being noticed in a month's revenue report.

003

Portal

Developers self-serve or they leave

Upgrades, downgrades, card updates and invoices in a branded portal on your own domain. A developer who has to email sales to raise a rate limit is a developer evaluating someone else.

004

B2B

Your customers are companies

Business buyers who enter a tax ID at checkout get a proper invoice by email, on the first charge and on every renewal — which is what their finance team will ask for before they can expense it.

Subscription records with plan tiers, usage charges and renewal dates for an API product. — Tiers, usage and renewals — the state your key issuer reads from.

Wiring billing to your API

01
Model the tiers

A product with an offer per tier, plus a usage price for the requests beyond the allowance.
02
Sell from your docs

The overlay opens over the pricing page in your documentation site, so an evaluating developer never leaves it.
03
Issue the key on the webhook

payment_success is the signal that money arrived. Mint or activate the key there, server-side.
04
Revoke on the way out

Cancellation and failed-payment events are what should throttle or disable a key, rather than a manual review.

Merchant of Record

You could do all of this yourself

Selling digital goods across borders means registering for tax in each market, wiring up a tax engine, and answering for every dispute. As your Merchant of Record, that is our name on the paperwork instead of yours.

What it takes

Fungies

Processor only

01 Tax registration

✓ None needed — we are already registered.

You register for VAT and sales tax per market.

02 Tax calculation

✓ Real-time rates on every transaction.

You wire up a tax engine and maintain it.

03 Remittance

✓ We file and pay the authorities directly.

You file monthly, quarterly, and annually.

04 Audits

✓ We answer the tax authority.

You keep the records and take the questions.

05 Chargebacks

✓ Disputes and fraud handled for you.

Your team fights each case.

06 Pricing

✓ One commission, only when you sell.

Processor fee plus tax software plus consultants.

07 Accounting

✓ You receive net revenue.

Gross receipts plus a tax liability to track.

What you get to skip building

Metered pricing: Pay-as-you-go and usage-based plans, without writing a rating engine or a monthly invoice job.
Proration on tier changes: Moving between plans mid-cycle is worked out to the day, and the next renewal can be previewed through the API first.
Signed webhooks: Payment success, refunded and failed, plus subscription created, interval, updated and cancelled — with retries and delivery history.
A REST API over everything: Products, offers, orders, payments, subscriptions, users, discounts and webhooks at api.fungies.io/v0.
Invoices for business buyers: Issued automatically when a tax ID is supplied at checkout, on the first charge and on each renewal.
Global tax, filed: VAT, GST and sales tax under our registrations as Merchant of Record, recalculated on every renewal.