There are many ways to know your balance. But we cannot, and should not, know when your account has a low balance since that will depend on your business rules. Anyhow, there are several ways to know your balance: 

1.- By going to your UNNAX Portal Accounts > Statements

2.- Using our API for Accounts Detail.

The response received from this endpoint will bring several information about your account. Among them you can find the account balance.

    "account_number": "ES9****************143",
    "updated": "2017-05-26 14:17:42",
    "account_hash": "3559******************503",
    "id": 25,
    "bank_data": {
      "bank_type": 999,
      "bank_state": true,
      "bank_read": true,
      "can_fast_transfer": true,
      "bank_transfer": true
    "name": "Cuenta Caixa Formulario",
    "displayed": true,
    "login_data": false,
    "state": 1,
    "pending_balance": 0,
    "credential_id": 171,
    "current_balance": 0,

3.- After each confirmed payout transaction, if you have configured the event webhook “event_payment_transfer_auto_processed”,  you will receive a callback that will include the balance of the account after the transaction has been confirmed

  "response_id": "bd9602**********************b10ad",
  "signature": "f5f519615****************46954ba4887be67d",
  "date": "2018-09-25 11:01:32",
  "service": "auto_transfer",
  "triggered_event": "event_payment_transfer_auto_processed",
  "environment": "unnax_integration_aws",
  "data": {
    "success": true,
    "product": "movex_dbt",
    "order_id": "1537873308",
    "bank_order_id": "1537873308",
    "date": "2018-09-25",
    "time": "11:01:32",
    "amount": 15500,
    "currency": "EUR",
    "customer_id": "1",
    "customer_account": "ES*******************17",
    "source_account": "ES******************22",
    "src_account_balance": 5228,
    "cancelled": false,
    "source_bank_id": 3
  "trace_identifier": "1537873308"

With this information you will be able to trigger any automatic response when your balance has reached a threshold.

 4.- You can also get notifications from your account, when it has gone below a threshold, by registering a Webhook for the event_low_balance_threshold event. You could receive notifications via email or callback and it will be triggered once the account reaches the configured threshold.