Links in this essay will take you to information about the usage experts and their work. Numbers in parentheses are page references in the sources.
Your grammar checker may accuse you of bad writing every time you choose a verb in the passive voice, but be assured that most usage experts will not. The rule that writers should "prefer" active verbs means just that: Use the active voice unless you have a good reason for choosing the passive.
ACTIVE [SUBJECT DOES THE ACTION]
The committee reached a decision.
PASSIVE [SUBJECT RECEIVES THE ACTION]
A decision was reached by the committee.
Why should we prefer active verbs? The experts agree on the reasons. Passive sentences are wordier than their active counterparts. They fail to emphasize or sometimes even name the actor (often deceptively, as in Top-secret information was inadvertently misplaced). And, in the words of Bryan Garner, the passive voice "subverts the normal word order for an English sentence, making it harder for readers to process the information" (613).
Usage experts also agree on the major exceptions to the rule. All agree that the passive is appropriate when the actor is unknown, obvious, or irrelevant. The passive also works well when the emphasis belongs on the receiver of the action, as in these examples, given by Richard Lederer and Richard Dowis:
The meeting was concluded after two hours of heated debate.
The criminal was arrested, tried, convicted, and sentenced to prison. (101)
In scientific writing, emphasizing the receiver of the action lends an air of scientific objectivity.
Participants in the study were asked to respond to a Rorschach test.
Occasionally the passive voice may be used to smooth a transition from old information to new (by placing old information in the subject position). The American Heritage Dictionary of English Usage offers a good example from a passage by astronomer Robert P. Kirschner:
. . . Eventually fuel runs out, and the inner core of the red giant congeals intoa white dwarf. A white dwarf is protected from total gravitational collapse not by the kinetic pressure of gases. . . . (58)
To sum up: There is nothing wrong grammatically with the passive voice, and for certain purposes it can be quite useful. So when your grammar checker flags a passive sentence, think carefully. If you have chosen the passive for a good reason, let it stand. If not, revise.
Source: Hacker Handbooks (Boston: Bedford, 2013).