Final answer:
Passive voice is useful in business communication when concealing the doer or when clarity is most important.
Step-by-step explanation:
In business communication, there are instances where the use of passive voice can be effective. One such instance is when you want to conceal the doer. This can be useful when you don't want to attribute blame or responsibility to someone explicitly. Another situation where passive voice can be useful is when clarity is most important. By using passive voice, you can focus on the action or result, without distracting the reader with the subject performing the action.