---
title: Billing Automation
category: product
entity_type: skill
price: $15
canonical: https://forgehouse.ai/skills/billing-automation/
lang: en
hreflang_alt: https://forgehouse.ai/tr/skiller/billing-automation/
last_updated: 2026-06-20
---

# Billing Automation

> Build automated billing systems for recurring payments, invoicing, subscription lifecycle, and…

A complete blueprint for building automated recurring-billing systems: subscription lifecycle, invoice generation, dunning recovery, proration, tax, and usage-based billing. It ships working Python patterns for the subscription state machine (trial, active, past_due, canceled, paused) and the billing-cycle engine that charges, generates invoices, and triggers recovery on failure. The goal is a billing pipeline that runs itself and stops leaking revenue.

## Use cases
- Implementing SaaS subscription billing with monthly, annual, or custom cycles
- Recovering failed payments with a staged dunning ladder and retry schedule
- Calculating fair proration for mid-cycle plan upgrades, downgrades, and seat changes
- Generating and delivering invoices as HTML or PDF with line items and tax
- Handling sales tax, VAT, and GST by customer jurisdiction
- Billing usage-based charges with tiered, per-unit, or volume pricing

## Benefits
- Recovered revenue from failed payments via a dunning escalation ladder that balances pressure and retention
- Lower involuntary churn by replacing hard lock-outs with grace periods on card expiry and gateway outages
- No duplicate charges, because idempotent invoicing makes retries and webhook duplicates safe
- Accurate books with deferred-then-recognized revenue handling for annual and monthly plans

## What’s included
- Subscription lifecycle state machine with trial, activation, past-due, and cancellation logic
- Billing-cycle engine: invoice generation, charge attempt, success and failure branches
- Dunning manager with day-3 / day-7 / day-14 retry schedule and templated notifications
- Proration calculator for plan changes and seat additions
- Tax calculator with jurisdiction detection (US sales tax, EU VAT, AU GST) and VAT validation
- Usage-based billing engine with tiered, per-unit, and volume pricing models

## Who it’s for
Backend engineers and SaaS builders implementing or automating subscription billing who need fair proration, resilient payment recovery, and correct tax handling.

## How it runs
Recurring billing is a state machine with money attached. Here is how a subscription moves from invoice generation through tax, idempotent charging, dunning and proration without ever double-billing a customer.
1. Models the subscription lifecycle as a state machine (trial, active, past_due, paused, canceled) so an invalid state transition can never fire a charge.
2. On each billing date it generates the invoice: the plan line item, usage-based charges if the plan is metered, then tax by jurisdiction (US sales tax, EU VAT, AU GST) before the invoice is finalized.
3. Charges the saved payment method with an idempotency key built from customer, billing period and plan, so a network retry or duplicate webhook can never double-bill.
4. On a failed charge it starts the dunning ladder: automatic retry first, then emails at day 3, 7 and 14, service restriction before cancellation, each step weighing recovery against churn.
5. Prorates mid-cycle plan changes by day: unused old-plan time is credited against the new-plan charge, and seat additions are billed only for the remaining days.
6. Logs every billing event to an audit trail and keeps the customer's service alive through a grace period while the payment issue is being resolved.

## FAQ
### Does this replace Stripe, or sit on top of a payment processor?
It's the billing logic above the processor: the subscription state machine, invoicing, dunning, and proration. You still need a processor underneath to actually charge cards; this models the system that decides what to charge and when.

### Proration is where billing quietly breaks. Does this really get upgrades and seat changes right?
It ships proration patterns built specifically for mid-cycle upgrades, downgrades, and seat changes. The fairness logic is encoded, but you have to wire it to your real plan definitions, it can't guess your pricing rules.

### Will it handle tax compliance across regions for me?
It treats tax as part of the billing model, but it isn't a jurisdiction-by-jurisdiction tax engine. For real multi-region compliance you pair it with a dedicated tax service; this gives you the hook, not the ruling.

## Price
$15, one-time, no subscription. VAT included.

Related guide: [AI for ecommerce](https://forgehouse.ai/guides/ai-for-ecommerce/)