core/homeassistant/components/monarch_money/icons.json

{
  "entity": {
    "sensor": {
      "sum_income": { "default": "mdi:cash-plus" },
      "sum_expense": { "default": "mdi:cash-minus" },
      "savings": { "default": "mdi:piggy-bank-outline" },
      "savings_rate": { "default": "mdi:cash-sync" }
    }
  }
}