Form and rules
How it works
The passive keeps the relevant tense/aspect in be and adds the past participle: is made, was being made, has been made.
Continuous passive uses being; perfect passive uses been.
Modal/future passive uses modal/will + be + past participle.
Use passive when the receiver/process/result is more important than the agent or the agent is unknown/unnecessary.
Include by + agent only when identifying the agent adds meaningful information.