Why is "Close currency balance" greyed out in TWS?

You can monitor your cash balances and convert the remaining non-base currency balance(s) into your base currency in the Trader Workstation (TWS) Account window:

1. In TWS, from the Account menu select Account Window
2. Scroll down to the…

If you selected USD as your base currency, your account values will be shown in USD even if you are holding foreign currency or products denominated in a different currency. If you would like to see your current currency balances, open the Account window by clicking the Account menu option followed by Account Window. Scroll down to the Market Value- Real FX Balance section and you will see all of your currencies listed and their respective balances…

You may see discrepancies in Total Cash versus Cash in Base Currency after making a trade in a non-base currency. The reason for the discrepancy is that additional time is needed for settlement to allow trades executed in a non-base currency to convert to the base currency. In order to see your Settled Cash balance, you will need to add the Settled Cash column to your Account Window under the Market Value - Real FX Balance section…

To see your actual, real-time currency balances, from the Account window in TWS or the Balances section of the Portfolio in IBKR Desktop, check the Total Cash and Settled Cash fields of the Market Value - Real FX Balance…