Advanced passive forms

In A technician repaired the lift, the subject tells us who did the action. In The lift was repaired yesterday, the lift becomes the subject and the technician can be left out. English uses the passive when the action, result or person affected matters more than the agent—or when the agent is unknown.

The basic form is be + past participle. The tense is carried by be:

The bridge is inspected every spring. (present routine)
The bridge was being inspected when we arrived. (past action in progress)
The bridge has been repaired. (present result)
The bridge will be reopened next week. (future)

The main verb stays in the past participle: built, chosen, written. Do not use a past form after be: ~~was wrote~~ → was written.

Convert the sentence without changing its time

Take The council is repairing the bridge. To make the bridge the subject:

Identify the receiver: the bridge.
Keep the present continuous meaning: is being.
Put the action in its participle form: repaired.

The result is The bridge is being repaired. The council can be added with by, but it is not necessary if the paragraph is about the bridge.

Active	Passive	Time or aspect preserved
They inspect the lift monthly.	The lift is inspected monthly.	Present routine
They are inspecting the lift.	The lift is being inspected.	Activity happening now
They inspected the lift yesterday.	The lift was inspected yesterday.	Completed past event
They had inspected it before we arrived.	It had been inspected before we arrived.	Earlier past event
They have inspected it.	It has been inspected.	Present perfect
They must inspect it.	It must be inspected.	Requirement

Do not change are repairing to was repaired simply because you are changing the voice. That would also change the time and whether the work is complete.

Being and been have different jobs

The car is being repaired puts us inside a repair in progress. The car has been repaired presents the repair as completed, with a result now. Being accompanies a continuous form; been is the participle of be, used after have/has/had.

For negatives, put not after the first auxiliary: It hasn't been repaired; It isn't being repaired. For questions, move that auxiliary before the subject: Has it been repaired?; Is it being repaired? The rest of the chain stays in place.

The agent is optional

Add by + agent when the person or organisation matters:

The mural was painted by local students.

Leave the agent out when it is obvious, unknown or unimportant:

My bike was stolen overnight.
The final decision was announced this morning.

A passive sentence should not hide responsibility if naming the person is relevant. Mistakes were made may be grammatical, but The team made two mistakes is clearer when the agent is known and matters.

Passive patterns with two objects

Some verbs take a direct and an indirect object: They gave every guest a map. Either object can become the subject of a passive:

Every guest was given a map.
A map was given to every guest.

The first is often more natural when the recipient is the topic. Verbs such as send, offer, teach, show and promise commonly allow this pattern. With some verbs, only one passive is natural, so do not assume every active sentence has two equally good passive forms.

Keep the preposition

A passive can be formed from a verb followed by a preposition:

Someone broke into the office. → The office was broken into.
They haven’t paid for the trip. → The trip hasn’t been paid for.

The preposition stays with the verb. Removing it changes the construction: ~~The office was broken~~ means someone damaged the office, not that someone entered it unlawfully.

Passive with modals and non-finite forms

After a modal, use be + past participle: The form must be signed, The files should have been saved. The perfect passive has have been + participle; the continuous passive has be being + participle (The road is being repaired). Very long forms such as has been being repaired are grammatically possible but uncommon; writers usually rephrase them.

Passive infinitives and gerunds are also useful: The issue needs to be discussed; She dislikes being interrupted; The files appear to have been altered. The passive always keeps the receiver of the action in focus.

Where a passive is useful—and where it is impossible

In a description of a manufacturing process, the passive keeps the product as the topic:

The olives are washed, pressed and filtered. The oil is then stored in sealed containers.

Repeating workers in every sentence would add little. In a personal achievement, an active subject may matter more: Our volunteers restored the garden credits the people involved. Neither voice is automatically better; choose the subject your reader needs to follow.

Ordinary passives require a suitable object or prepositional complement in the active construction. Someone stole my bag allows My bag was stolen. The accident happened at noon does not allow ~~The accident was happened~~: nothing receives the action of happen. Likewise, The guests arrived, not ~~were arrived~~.

Finally, by identifies an agent, whereas with usually identifies an instrument: The door was opened by the caretaker with a spare key. These phrases answer different questions: Who did it? What did they use?