1. The same framework, a new time layer
In the neighbouring rule, you saw the chain modal + be + past participle for evaluating what is happening now or is to happen: can be fixed, must be signed. This rule adds one more link—have been—and shifts the same evaluation into the PAST: something has already happened (or has not happened), and we are talking about it now.
The form becomes longer (modal + have been + V3 instead of modal + be + V3), but the meaning of the modal verb often changes with it: must in the present passive most often means obligation (“must be signed”—it is necessary to sign it), while must in this chain means a CONFIDENT DEDUCTION about the past (“must have been signed”—it was probably already signed).
The lights are still on, so the office must have been left unlocked overnight.
The lights are still on, so the office must have been left unlocked overnight.
We evaluate a past event based on present evidence (the lights are on).
The window should have been closed before the rain started.
The window should have been closed before the rain started.
A reproach for something that, judging from the context, was not done on time.
2. Form: modal + have + been + V3
Keep the order modal + have + been + V3. Not and adverbs can stand between the links: might not have been sent, must have already been checked. After a modal, have does not change to has or had; in this simple perfect passive, we use been.
This is the same principle that applies to any verb after a modal: can go, must stop—and likewise can have gone, must have stopped. Here, one more link (been) is simply added between have and the participle to change the active perfect into a passive one.
Regular verbs form V3 with -ed (fix → fixed, check → checked); irregular verbs have their own forms (steal → stolen, leave → left, break → broken). Some V3 forms are the same as the base form: cut → cut. The longer construction have been being checked also exists, but it is the perfect continuous passive and is outside the main pattern of this lesson.
modal + have + been + V3 (have and been always remain in this form, whatever the subject)
- subject / S —
- The grammatical subject: who or what the clause is about; the verb agrees with it. In The book was written, the book is the subject, although someone else does the action.
- V3 / past participle —
- The third verb form: worked, gone, seen. Used after have/has or in the passive, for example; it is not always the same as V2.
- modal —
- A modal verb expresses meanings such as ability, possibility or necessity: can, may, must.
These photos might have been taken with a professional camera.
These photos might have been taken with a professional camera.
Might have been taken—all four links are present, and none has changed.
The missing key could have been left inside the office by accident.
The missing key could have been left inside the office by accident.
Left—the irregular participle (leave-left-left) comes directly after been.
3. Confident deduction and confident negative conclusion: must / can't / couldn't
Must have been + V3 means that the speaker is almost certain: the evidence points to this particular conclusion. This is no longer an obligation (as in must be done in the present passive), but a logical conclusion about what most likely happened.
For the conclusion “this could not have happened,” can’t / couldn’t have been + V3 are natural. Must not / mustn’t have can also express a negative conclusion in some varieties of English, so we should not declare it always incorrect. For a clear, neutral contrast, we compare must have with can’t have here.
The coffee machine must have been switched off by the last person to leave.
The coffee machine must have been switched off by the last person to leave.
A confident conclusion based on the fact that the machine is switched off now.
That email can't have been sent from her old account — she closed it months ago.
That email can't have been sent from her old account—she closed it months ago.
A confident negative conclusion: can't/couldn't, not mustn't.
4. Uncertain possibility: may / might / could
May, might, and could have been + V3 can express an uncertain deduction. In this context, they are often interchangeable, but could have been can also describe an unrealised possibility rather than an assumption about what actually happened. The meaning is determined by the whole situation.
These forms naturally appear when there are several possible explanations at the same time: the speaker may list two or three possibilities in succession, each with its own might/could have been, without finally choosing one.
The plants might have been watered by my neighbour while I was away.
My plants might have been watered by my neighbour while I was away.
An uncertain but plausible deduction without direct evidence.
This mark on the table could have been caused by a hot cup.
This mark on the table could have been caused by a hot cup.
Could have been—one of several possible causes, not the only one.
5. Reproach and an unfulfilled expectation: should / shouldn't
Should have been + V3 can evaluate an unfulfilled obligation or a desired past action: The tickets should have been booked, but they weren’t. It can also express an expectation when the result is not known: The parcel should have been delivered by now—we expect the parcel to have arrived already.
In a reproach, shouldn’t have been + V3 usually means that the action was carried out even though it should not have been. However, the form itself does not always prove that the action happened: in a context of supposition, it can express an expected absence of an action. First determine the speaker’s intention.
The tickets should have been booked weeks ago, before the prices went up.
The tickets should have been booked weeks ago, before the prices went up.
The expected action, judging from the context, was not completed on time.
This comment shouldn't have been left on a public page — it named a real client.
This comment shouldn't have been left on a public page—it named a real client.
The action has already been carried out (the comment was posted), and the speaker considers this a mistake.
6. From active to passive, negatives, and questions
In the active modal perfect, the agent is the subject: They must have cancelled the order. In the passive, the object becomes the subject: The order must have been cancelled. The agent can be added with by if it is important. This is a modal construction with a perfect, not the Past Perfect tense with had.
In a negative statement, not attaches directly to the modal verb (shouldn't, shouldn't have been); can't and couldn't are already negative and do not need a separate not. In a question, the modal verb comes before the subject, while have been + participle remain together immediately after it: “Could this have been avoided?”
Could the delay have been avoided if we'd started earlier?
Could the delay have been avoided if we'd started earlier?
Question: modal—subject—have been—participle.
The estimate shouldn't have been sent without the manager's approval.
The estimate shouldn't have been sent without the manager's approval.
Not comes immediately after should; the action has already been carried out—this is a reproach.
7. Scope of the rule: related constructions not practised here
Simple can be fixed and must be signed often refer to the present or future; could be fixed can also describe a past possibility. The perfect block have been + V3 gives a view of an earlier action. It can sometimes place that action before a future deadline: It must have been completed by next Friday. Here, we focus on evaluating the past.
Would have been + V3 (an unreal condition: if… then it would have been done) belongs to the third conditional, not to evaluating a real past event—it has a different logic and a different modal. The causative construction have/get something done (arrange for something to be done for you) is a separate category, Causative, not a passive with a modal.
This form must be signed before Friday.
This form must be signed before Friday.
A present requirement (must be)—not the focus of this rule; compare it with “must have been signed”.
If we'd known earlier, the trip would have been cancelled.
If we'd known earlier, the trip would have been cancelled.
An unreal condition (the third conditional)—a different construction, not the focus of this rule.
8. Transfer to real communication: several meanings in one utterance
In real explanations, reports, or everyday conversations, these meanings naturally occur together: one sentence expresses a deduction about a cause, and another expresses a reproach for something that was or was not done. The aim of this rule is to switch consciously between them without confusing the form.
The same framework have been + V3 is repeated with every modal verb, so there is no new form to learn—only the need to consciously choose the modal verb for the meaning you want to convey at that moment.
The delivery must have been delayed somewhere — it should have arrived by Tuesday.
The delivery must have been delayed somewhere—it should have arrived by Tuesday.
A confident deduction (must have been) and a reproach for an unfulfilled expectation (should have) in one utterance.
I can't have been the only one who noticed — someone else should have said something.
I can't have been the only one who noticed—someone else should have said something.
Both parts here are active: have been the only one—the perfect of be with a noun complement; should have said—the active perfect. This contrast helps with recognition: have been by itself does not make a sentence passive.
Common mistakes
Incorrect:The contract should been signed by both parties before the deadline.
Correct:The contract should have been signed by both parties before the deadline.
have is missing: have must always come between should and been, whatever modal verb is used.
Incorrect:The invoice must have sent to the wrong department.
Correct:The invoice must have been sent to the wrong department.
been is missing: the invoice cannot send something by itself; a passive is needed here, not an active perfect without an object.
Incorrect:The results can't have be announced yet.
Correct:The results can't have been announced yet.
After have, been is required in this passive perfect. Can’t have been announced expresses the conclusion that the results could not yet have been announced.
Incorrect:The car should have been fix before the trip.
Correct:The car should have been fixed before the trip.
After been, a participle (fixed) is required, not the base form of the verb (fix).
Incorrect:The staff should be told about the delay yesterday.
Correct:The staff should have been told about the delay yesterday.
The time marker yesterday requires an evaluation of the past (should have been), not a present modal passive (should be).
Incorrect:This must to have been a mistake.
Correct:This must have been a mistake.
Modal verbs do not take to before the following verb.