--- title: "Billing for API and developer products · Fungies" description: "Usage-based billing for an API product — tiers, overages, proration and API keys tied to subscription state through signed webhooks." image: "https://fungies.io/og-image.jpg" canonical: "https://fungies.io/solutions/api-products/" --- 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. [Start free](https://app.fungies.io/register) [Book a demo](https://calendly.com/duke-vuh/fungies-io-demo-clone) No upfront costs. No credit card required. Already selling with Fungies [![Leadsin.io](/logos/clients/leadsin.png)](/customer-story/hosted-checkout-solution-for-leadsin-io-a-saas-business "Leadsin.io — read the story")[![RenderAI](/logos/clients/renderai.png) ](/customer-story/helping-renderai-reduce-their-ai-saas-payment-integration-from-days-to-just-a-couple-of-minutes "RenderAI — read the story")[![SuperScale](/logos/clients/superscale.png) ](/customer-story/nimblebits-revenue-boost-with-a-web-store-solution "SuperScale — read the story")[![FreeVocals](/logos/clients/freevocals.png) ](/customer-story/freevocals-com-and-fungies-io-a-seamless-solution-for-digital-e-commerce "FreeVocals — read the story")![STATSCORE](/logos/clients/statscore.png)![SimFabric](/logos/clients/simfabric.png)![BotRix](/logos/clients/botrix.png)![Enhance AI](/logos/clients/enhance-ai.png)![The Humanize AI](/logos/clients/humanize-ai.png)![Kenerate AI](/logos/clients/kenerate.png) 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.](/_astro/subscriptions.CS4yi8pK_1kMw30.webp?dpl=dpl_8EZJmbvb3ugYq7WK1KgC21BX19Zp) Tiers, usage and renewals — the state your key issuer reads from. ## Wiring billing to your API 1. 01 ### Model the tiers A product with an offer per tier, plus a usage price for the requests beyond the allowance. 2. 02 ### Sell from your docs The overlay opens over the pricing page in your documentation site, so an evaluating developer never leaves it. 3. 03 ### Issue the key on the webhook payment\_success is the signal that money arrived. Mint or activate the key there, server-side. 4. 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. Pricing 5% + 50¢ per sale, and nothing else Negotiable at higher sales volume. [See full pricing →](/pricing) [Start free →](https://app.fungies.io/register) ## No monthly fee. No minimum. No card to get started. One rate covers the whole stack. There is no tier that unlocks tax filing and no add-on for the store builder. - ✓ Payment processing - ✓ Tax calculation and filing - ✓ Fraud screening - ✓ Chargeback handling - ✓ Store builder and hosting - ✓ Every platform feature ## Teams like yours, already shipping [All customer stories →](/case-studies-customers) [ AI SaaS Canada ### TextToVideo.bot Weeks of payment work, done in minutes An AI video generation platform launched its subscription business without writing a payment integration at all. Minutes to stand up subscription plans Read the story →](/customer-story/how-fungies-enabled-texttovideo-bot-to-integrate-payments-in-minutes)[ AI SaaS Uruguay ### RenderAI From days of integration to a couple of minutes An AI image platform replaced a slow manual payment process with three subscription tiers and an overlay checkout. Minutes to replace a days-long integration Read the story →](/customer-story/helping-renderai-reduce-their-ai-saas-payment-integration-from-days-to-just-a-couple-of-minutes)[ SaaS Miami, Florida, USA ### Leadsin.io A hosted checkout with no payment infrastructure to build A lead generation platform started taking monthly and yearly subscriptions without standing up any payment infrastructure of its own. Zero tax registrations of their own Read the story →](/customer-story/hosted-checkout-solution-for-leadsin-io-a-saas-business) ## API product questions ### Can I charge per request rather than per month? ### How do I keep API keys in step with billing? ### Do business customers get invoices? ### Can I preview what a plan change will cost? ### Is there tooling beyond the REST API? ## More for SaaS teams - [SaaS companies → Sell subscriptions worldwide with no tax registrations.](/solutions/saas) - [AI products → Credit packs, metered usage, and costs that move per call.](/solutions/ai-saas) - [Solo founders → Sell worldwide without a finance function behind you.](/solutions/indie-saas) ## Charge for the API without building a rating engine Model the tiers, wire the webhook to your key issuer, and run a full cycle in sandbox before anyone is billed. [Start free](https://app.fungies.io/register) [Book a demo](https://calendly.com/duke-vuh/fungies-io-demo-clone) No upfront costs. No credit card required. ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://fungies.io/#organization","name":"Fungies","legalName":"Fungies Inc.","url":"https://fungies.io/","description":"Merchant of Record for SaaS, games, and digital products. Fungies handles global payments, VAT and sales tax, and checkout. 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Fungies handles global payments, VAT and sales tax, and checkout. Free to start, commission only.","inLanguage":"en","publisher":{"@id":"https://fungies.io/#organization"}},{"@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://fungies.io/"},{"@type":"ListItem","position":2,"name":"Solutions","item":"https://fungies.io/solutions"},{"@type":"ListItem","position":3,"name":"Billing for API and developer products","item":"https://fungies.io/solutions/api-products"}]},{"@type":"FAQPage","mainEntity":[{"@type":"Question","name":"Can I charge per request rather than per month?","acceptedAnswer":{"@type":"Answer","text":"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."}},{"@type":"Question","name":"How do I keep API keys in step with billing?","acceptedAnswer":{"@type":"Answer","text":"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."}},{"@type":"Question","name":"Do business customers get invoices?","acceptedAnswer":{"@type":"Answer","text":"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."}},{"@type":"Question","name":"Can I preview what a plan change will cost?","acceptedAnswer":{"@type":"Answer","text":"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."}},{"@type":"Question","name":"Is there tooling beyond the REST API?","acceptedAnswer":{"@type":"Answer","text":"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."}}]}]} ```