Recurring billing engine for SaaS products: plans with seats and metered add-ons, trials, coupons, mid-cycle changes with exact proration, period invoicing with VAT, card dunning, signed webhooks and MRR/churn metrics driven by an injectable clock.
This page is a static API reference built from the service's exported OpenAPI document on every push to main; there is no backend behind it, so requests cannot be sent from here. Open the Codespace to run the real service with demo data, or deploy your own copy to Render. All /v1 routes need X-API-Key (change-me in the Codespace), which seeds demo plans, a coupon and five customers with billing seed.