Billing Automation

Master automated billing systems including recurring billing, invoice generation, dunning management, proration, and tax calculation.

When to Use This Skill

Implementing SaaS subscription billing
Automating invoice generation and delivery
Managing failed payment recovery (dunning)
Calculating prorated charges for plan changes
Handling sales tax, VAT, and GST
Processing usage-based billing
Managing billing cycles and renewals

Core Concepts

1. Billing Cycles

Common Intervals:

Monthly (most common for SaaS)
Annual (discounted long-term)
Quarterly
Weekly
Custom (usage-based, per-seat)

2. Subscription States

text

trial → active → past_due → canceled
              → paused → resumed

3. Dunning Management

Automated process to recover failed payments through:

Retry schedules
Customer notifications
Grace periods
Account restrictions

4. Proration

Adjusting charges when:

Upgrading/downgrading mid-cycle
Adding/removing seats
Changing billing frequency

Quick Start

python

from billing import BillingEngine, Subscription

# Initialize billing engine
billing = BillingEngine()

# Create subscription
subscription = billing.create_subscription(
    customer_id="cus_123",
    plan_id="plan_pro_monthly",
    billing_cycle_anchor=datetime.now(),
    trial_days=14
)

# Process billing cycle
billing.process_billing_cycle(subscription.id)

Detailed patterns and worked examples

Detailed pattern documentation lives in references/details.md. Read that file when the navigation tier above is insufficient.