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

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

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

Detailed patterns and worked examples

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