In passive sentence constructions, the object of your sentence comes first and the subject of your sentence comes at the end. While passive voice isn't grammatically incorrect, it makes your writing less direct and clear.
Here's an example of passive voice:
In this sentence, the dog, the object, comes before Joe, the subject. It's much clearer and simpler to say "Joe walked the dog."
When you use passive voice, you need to wait til the end of the sentence to find out who's doing the action. Using passive voice also removes the power from your writing. By using an active verb and putting the subject of your sentence up front, you give your writing more power.
Sometimes, you'll need to use passive voice because the subject of the sentence isn't known or doesn't matter. But most of the time, you'll want to use active voice. We recommend having less than 50 instances of passive voice per every 1,000 sentences in your writing.
Passive voice can be unclear. With passive voice, you can construct a grammatically correct sentence without showing who or what is performing the action.
This sentence is grammatically correct because it has a subject (“the book”) and a verb (“was read”). But who read it? It feels unsatisfying and the reader won't have an appropriate picture in their heads.
Depending on the context, passive voice can your sentence open for interpretation by the reader, making them uncertain who or what is performing the action in the sentence.
Consider these examples:
Who made the error: you, or the bank, or some nefarious person bent on ill intent?
When something happens and it's unclear who did it, passive voice is often preferred:
Since we don't exactly know the subject of these sentences, it's appropriate to use passive voice. As you can see with the first two examples, passive voice often fits well with unsolved crimes.
Passive voice is also okay when the doer of an action is irrelevant:
In this case, we're not concerned with who unveiled the statue, we're concerned with when the statue was unveiled. That makes passive voice okay.
Passive voice is more acceptable in certain genres of writing, like academic or business writing. As the writer, you can choose whether or not to remove instances of passive voice from your work.