Utility Customer and Billing Schema

erDiagram
  CUSTOMER ||--o{ ACCOUNT : holds
  PREMISES ||--o{ ACCOUNT : "billed for"
  PREMISES ||--o{ METER : has
  METER ||--o{ READING : records
  ACCOUNT ||--o{ BILL : receives
  TARIFF ||--o{ BILL : "priced by"
  BILL ||--|{ BILL_LINE : contains
  BILL ||--o{ PAYMENT : "paid by"
  CUSTOMER {
    int id PK
    string name
    string phone
  }
  ACCOUNT {
    int id PK
    int customer_id FK
    int premises_id FK
    string status
  }
  PREMISES {
    int id PK
    string address
    string category
  }
  METER {
    int id PK
    int premises_id FK
    string serial_no
    date installed_on
    date removed_on
  }
  READING {
    int id PK
    int meter_id FK
    datetime read_at
    decimal kwh
    string read_type
  }
  TARIFF {
    int id PK
    string code
    decimal rate_per_kwh
    date effective_from
  }
  BILL {
    int id PK
    int account_id FK
    int tariff_id FK
    date period_end
    decimal amount
  }
  BILL_LINE {
    int id PK
    int bill_id FK
    string description
    decimal amount
  }
  PAYMENT {
    int id PK
    int bill_id FK
    decimal amount
    string channel
  }