Do I ALWAYS have to write in active voice?
No, you don’t! Although writing in active voice is generally preferable, sometimes passive voice is the better choice, or maybe even the only choice.
When you write in active voice, the subject of the sentence accomplishes the action:
The technician checked the equipment for leaks.
The subject (technician) performs the action (checked the equipment for leaks).
But what if you don’t know who performed the action? Or what if the action itself is more important than who did it?
The equipment had been checked for leaks.
The most important thing is that the equipment was checked for leaks. And besides, I may not know exactly who did it.
So here’s the deal: Write in active voice when possible. It is more direct and normally uses fewer words to make a point, so active voice is generally the better choice.
However, when you don’t know who accomplished the action, or when what happened is more important than who did it, passive voice is the way to go.