BillFlow
Automated Billing & Invoicing Platform
About the Project
BillFlow is a billing and invoicing platform built for service businesses and subscription companies that need automated billing cycles, multi-currency support, and seamless payment collection. The platform handles everything from quote generation through invoice delivery, payment processing, and revenue recognition.
With integrations across multiple payment gateways and accounting systems, BillFlow eliminates manual billing workflows, reduces payment collection time, and ensures tax compliance across jurisdictions. The customer portal gives clients self-service access to their billing history and payment methods.
Requirements & Objectives
- Implement automated recurring billing with configurable cycles (weekly, monthly, quarterly, annual).
- Integrate multiple payment gateways including Stripe, PayPal, and bank transfers.
- Build tax calculation engine supporting GST, VAT, and sales tax across jurisdictions.
- Generate professional invoices with customizable templates and branding.
- Provide customer self-service portal for viewing invoices, updating payment methods, and downloading receipts.
- Deliver financial reporting with revenue recognition, aging reports, and cash flow projections.
The Engineered Solution
1Billing Automation Engine
Configurable billing cycle management that automatically generates invoices, applies taxes, sends reminders, and processes payments on schedule without manual intervention.
2Payment Gateway Hub
Unified payment processing layer abstracting multiple gateways, enabling clients to pay via credit card, ACH, PayPal, or bank transfer with automatic reconciliation.
3Tax Compliance Module
Jurisdiction-aware tax engine that calculates and applies the correct GST, VAT, or sales tax based on buyer and seller locations with audit-ready reporting.
4Customer Billing Portal
White-labeled self-service portal where customers view invoices, update payment methods, download receipts, and manage their subscription plans.
System Architecture & User Flow
Engineering Process
- Mapped billing workflows for subscription, usage-based, and one-time billing models.
- Designed multi-tenant architecture with isolated billing data and configurable branding.
- Built billing engine with automated invoice generation and payment scheduling.
- Integrated Stripe and PayPal with unified webhook handling and reconciliation.
- Developed tax calculation engine with jurisdiction lookup and rate management.
- Created customer portal with secure authentication and self-service capabilities.
Production Tech Stack
| Layer / Component | Production Technologies |
|---|---|
| Frontend | Next.jsTypeScriptTailwind CSS |
| Backend | Node.jsExpress |
| Database | PostgreSQL |
| Payments | StripePayPal SDK |
| Queue | Bull (Redis) |
| PDF Generation | Puppeteer |
Outcome & Business Impact
BillFlow reduced average payment collection time from 34 days to 8 days and eliminated 95% of manual billing tasks, freeing finance teams to focus on strategic work instead of chasing invoices.
