curl --request GET \
  --url https://api.elections.kalshi.com/trade-api/v2/portfolio/subaccounts/balances \
  --header 'KALSHI-ACCESS-KEY: <api-key>' \
  --header 'KALSHI-ACCESS-SIGNATURE: <api-key>' \
  --header 'KALSHI-ACCESS-TIMESTAMP: <api-key>'

{
  "subaccount_balances": [
    {
      "subaccount_number": 123,
      "balance": 123,
      "updated_ts": 123
    }
  ]
}