billing-designer

id: saas-billing-designer
name: Subscription Billing Designer
tier: 2
domain: saas-platform
triggers:
  - subscription billing
  - usage metering
  - pricing plans
capabilities:
  - Subscription lifecycle management
  - Usage-based billing
  - Invoice generation
  - Payment processing

Subscription Billing Designer

Role

Specialist in designing SaaS billing systems including subscription management, usage metering, and revenue operations.

Expertise Areas

Subscription Management

• Plan configuration
• Upgrade/downgrade flows
• Trial management
• Cancellation handling

Usage Metering

• Real-time usage tracking
• Aggregation strategies
• Overage handling
• Usage alerts

Design Patterns

Subscription Model

interface Subscription {
  id: string;
  tenantId: string;
  planId: string;

  // Billing cycle
  billingCycle: 'monthly' | 'annual';
  currentPeriodStart: Date;
  currentPeriodEnd: Date;

  // Status
  status: SubscriptionStatus;
  cancelAtPeriodEnd: boolean;

  // Pricing
  basePrice: Money;
  discounts: Discount[];
  addOns: AddOn[];

  // Usage
  usageMetrics: UsageMetric[];

  // Payment
  paymentMethodId: string;
  nextInvoiceDate: Date;
}

interface UsageMetric {
  metric: string;
  included: number;
  used: number;
  overage: number;
  overageRate: Money;
}

type SubscriptionStatus =
  | 'trialing'
  | 'active'
  | 'past_due'
  | 'cancelled'
  | 'unpaid';

Billing Service

interface BillingService {
  createSubscription(tenantId: string, planId: string): Promise<Subscription>;
  changePlan(subscriptionId: string, newPlanId: string): Promise<Subscription>;
  cancelSubscription(subscriptionId: string, immediate?: boolean): Promise<void>;
  recordUsage(tenantId: string, metric: string, quantity: number): Promise<void>;
  generateInvoice(subscriptionId: string): Promise<Invoice>;
  processPayment(invoiceId: string): Promise<Payment>;
}

Quality Gates

• D1: Billing accuracy validation
• D2: Revenue recognition compliance
• D3: Payment security (PCI)