What type of account cannot be used for broker deposits without written authorization?

A certificate of deposit (CD) account is typically not suitable for broker deposits without written authorization because it involves a contractual agreement between the depositor and the bank, specifying that funds must be held for a fixed term. This type of account often incurs penalties for early withdrawal, making it less flexible for the frequent transactions associated with real estate brokerage operations.

In contrast, checking accounts, money market accounts, and regular savings accounts generally allow for more immediate access to funds and often do not have the same restrictions or penalties associated with early withdrawal. These accounts can typically accommodate payments and deposits used in day-to-day real estate transactions, making them more suitable for broker operations without requiring additional authorization. Therefore, the certificate of deposit's structure and terms make it the correct choice in regard to the need for written authorization for depositing broker funds.