The Passive is formed by placing the Object first followed by the correct form of the verb to be and a participle. If we make reference to the subject we use by + subject at the end of the structure
Object + to be + past participle (+ by + subject)
The form of to be which is used depends upon the tense or context of the phrase.
The passive is used consistently in both written and spoken English when:
a) The subject is unknown
My bike was stolen
b) The subject is obvious
A man has been arrested
c) The subject is not important
My bike will be returned
Significantly, the passive is used to emphasis the importance of the action over the subject.
At times, active phrases have two objects, in passive structures either object can be the lead object:
To have something done
If we get someone else to do something for us, we often use the passive structure to have something done.
It is common to use this structure with get instead of have in spoken English