Cash balances in accounts do not earn interest. A lot of clients park their money temporarily in Money Market Mutual Funds (minimum $1,000 purchase and subsequent purchases of $1,000). There is no minimum holding period and no fee to buy or sell. Simply go to Trade → Mutual Fund to enter the order. The trade settles in one business day.
If you don’t want to purchase Money Market Mutual Funds, another option is to deposit them into a High Interest Savings Accounts (HISA).