Modal perfect passive (must have been done)
Modal perfect passive (must have been done) means “Modal perfect passive: modal + have been + past participle, a passive guess or judgement about the past”. Modal + have been + past participle is the passive way to guess or judge what happened earlier: It must have been stolen (I'm sure it was). Formation: modal + have been + past participle
Modal perfect passive: modal + have been + past participle, a passive guess or judgement about the past
B2Formation
modal + have been + past participle
Explanation
Modal + have been + past participle is the passive way to guess or judge what happened earlier: It must have been stolen (I'm sure it was). The modal shows how certain you are — must (near-certain), may, might or could (possible), can't (impossible) — while have been + participle keeps the past passive meaning. The subject received the action, and who did it is unknown or unimportant.
Examples
Note
Keep the doer out unless it adds information; if the agent is central, an active modal perfect is clearer: Someone must have taken it rather than It must have been taken by someone.
FAQ
Modal perfect passive (must have been done) — what does it mean and how is it used?
Modal perfect passive: modal + have been + past participle, a passive guess or judgement about the past. Modal + have been + past participle is the passive way to guess or judge what happened earlier: It must have been stolen (I'm sure it was). The modal shows how certain you are — must (near-certain), may, might or could (possible), can't (impossible) — while have been + participle keeps the past passive meaning. The subject received the action, and who did it is unknown or unimportant.
Modal perfect passive (must have been done) — how do you form it?
modal + have been + past participle
Modal perfect passive (must have been done) — any usage notes?
Keep the doer out unless it adds information; if the agent is central, an active modal perfect is clearer: Someone must have taken it rather than It must have been taken by someone.