Subscription Billing Platform

Part of the worlds-biggest-software-project initiative.

An AI-native, open-source subscription billing platform unifying usage-based metering, ASC 606 revenue recognition, and intelligent dunning in one engine.

The Subscription Billing Platform is a developer-first billing system for SaaS, AI, and cloud-infrastructure companies that need flexible recurring, usage-based, and hybrid pricing without paying enterprise vendor pricing. It targets engineering and finance teams who today are forced to choose between a proprietary suite (Zuora, Chargebee, Stripe Billing) or to stitch together open-source metering with manual revenue recognition.

Why Subscription Billing Platform?

Enterprise platforms like Zuora start at ~$75K/year and can exceed $500K/year, with implementation timelines of 6–18 months — pricing out most growth-stage SaaS companies.
Stripe Billing, Chargebee, and Recurly charge a percentage of billing volume (0.7%–0.75%) or thousands per month, scaling cost directly with revenue rather than usage.
Lago is the only mature open-source option but lacks ASC 606 automation, AI dunning, and enterprise contract modelling; its AGPLv3 licence creates friction for ISVs embedding billing in commercial products.
All current dunning systems use static retry schedules; per-customer behavioural learning to optimise retry timing and channel has not been shipped by any incumbent.
Following Stripe's 2024 acquisitions of Metronome and Orb, the usage-billing stack is consolidating under a single proprietary vendor — leaving an open alternative underserved.

Key Features

Subscription & Pricing Engine

Flexible subscription lifecycle: create, amend, pause, cancel, renew with proration and mid-cycle amendments
Hybrid pricing models: flat recurring plus usage overage in a single invoice
Graduated, package, percentage, volume, and tiered pricing rules
Prepaid credit ledgers and wallet management for commit-based contracts
Grandfathering and plan migration tools for pricing changes

Real-Time Usage Metering

Event ingestion and aggregation engine designed for high-throughput consumption pricing
Idempotent event ingestion with replay guarantees
Customer-facing real-time usage dashboards and invoice previews
Pricing simulation engine to model revenue impact of pricing changes against historical data before rollout

Revenue Recognition & Finance

Deferred revenue schedules with period-end recognition reports
ASC 606 / IFRS 15 automation including multi-element arrangement decomposition and variable-consideration handling
Auditable journal entry generation
SaaS metrics dashboards: MRR, ARR, churn, LTV, CAC cohort analysis
ERP and accounting sync (NetSuite, QuickBooks, Xero)

Dunning & Payments

Configurable retry schedules, notification templates, and payment fallback routing
Multi-gateway support (Stripe, Adyen, Braintree, GoCardless, PayPal)
Hosted checkout pages and customer self-service portal for plan and payment-method management
Multi-currency invoicing with tax line-item passthrough via external tax engines

Integrations & API

REST API with idempotent event ingestion, webhook emission, and comprehensive audit log
Pre-built connectors for Salesforce, HubSpot, NetSuite, QuickBooks
Self-hosted deployment with full data residency control

AI-Native Advantage

AI is integrated where incumbents rely on static rules or manual finance work. Intelligent dunning learns per-customer payment behaviour — card type, time of day, retry history — to optimise retry timing and channel, targeting recovery rates above the 60–70% industry baseline. An AI engine decomposes multi-element ASC 606 contracts and allocates transaction prices, eliminating days of finance effort per period close. Pricing recommendation analyses usage patterns and willingness-to-pay signals to suggest tier structures, while churn prediction surfaces usage-decline and failed-payment risk weeks before cancellation.

Tech Stack & Deployment

The platform is designed API-first with self-hosted (Docker / Kubernetes) and managed-cloud deployment options. Payment processing integrates with Stripe, Adyen, Braintree, GoCardless, and PayPal via tokenisation to maintain PCI DSS Level 1 posture without direct card storage. Standards alignment includes ASC 606 / IFRS 15 for revenue recognition, SEPA for European direct debit, ISO 20022 for international payment messaging, and SOC 2 Type II as a target operational baseline. Webhooks and a comprehensive REST API drive integration with downstream CRM, ERP, and data-warehouse systems.

Market Context

The global subscription billing management market was valued at ~$9.16B in 2025 and is projected to reach $37.36B by 2035 (Astute Analytica), with cloud-based solutions representing roughly 75% of the market and usage-based billing growing fastest. Incumbent pricing ranges from 0.7% of volume (Stripe Billing) and ~$599/month (Maxio) to ~$75K/year (Zuora mid-market) and $200K–$500K+/year (Zuora enterprise). Primary buyers are SaaS founders and CTOs at seed–Series B companies, VPs of Finance at $5M–$50M ARR mid-market SaaS, enterprise revenue operations leaders, and AI/cloud infrastructure companies with high-volume metered billing.

Project Status

This project is in the research and specification phase.
Contributions, feedback, and domain expertise are welcome.

Contributing

We welcome contributions from developers, domain experts, and potential users. See CONTRIBUTING.md for guidelines.

Important: All contributions must be your own original work or clearly attributed open-source material with a compatible licence. Copyright infringement and licence violations will not be tolerated and will result in immediate removal of the offending contribution. If you are unsure whether a piece of code, text, or other material is safe to contribute, open an issue and ask before submitting.

Licence

Licence to be determined. See discussion for context.