Passive with Modals

The basic order is modal verb, be, and past participle (V3). Not or adverbs can appear between these elements: should not be changed, must be carefully checked. Be after can, must, should, and the other listed modals does not change to is, are, or was.

This follows the same principle as any verb after a modal: can go, must stop, should wait — and similarly can be done, must be stopped, should be checked.

Regular verbs add -ed: check → checked, finish → finished, allow → allowed. Irregular verbs have their own past participles to learn: write → written, take → taken, send → sent, break → broken.

Be + -ing normally forms an active continuous construction: should be checking describes someone doing the checking. A continuous passive needs being + V3: should be being checked. The simple passive takes V3, which does not necessarily end in -ed or -en: cut → cut, put → put.

In a negative, not attaches directly to the modal, in a full form — must not, cannot, should not — or a contraction — mustn't, can't, shouldn't. The following be and participle do not change.

Unlike ordinary verbs, these modals do not need don't/doesn't/didn't: they form negatives without auxiliary do.

In a yes/no question, put the modal before the subject: Can the file be opened? Be and V3 retain their order, although an adverb can come between them: Can it be easily opened?

If asking about time, place, or manner, put the question word before the modal: When should the results be announced? In a question about the subject itself, there is no additional subject: What should be changed?

Add a by-phrase only when the performer matters to the meaning or is not recoverable from context: exactly who must approve, sign, or carry out something.

If the performer is generic — people in general or any staff member — or obvious, the by-phrase is naturally omitted. Rules, notices, and instructions commonly take this form.

Each modal — can, could, may, might, must, and should — contributes its own meaning, such as permission, advice, obligation, or possibility. We do not compare these meanings in detail here; that belongs to the related rule “Common modal passives” in the same topic.

To make a deduction or judgment about a completed past event, use modal + have been + V3: must have been done expresses a deduction that it was done; should have been done says it ought to have been done. The simple framework with could can also refer to a past possibility: The door could be opened with a key. Context and the modal's meaning determine time, not the mere presence of be.

The causative construction have/get something done, such as have your hair cut, belongs to a different category: causatives, rather than modal passives.

In real notices, instructions, and rules, several modal passives naturally appear together: one sentence expresses an obligation, another permission or advice. Moving comfortably between them is this rule's goal.

The same be + participle framework recurs after each modal, so there is no new structure to learn; simply choose the modal that fits the meaning.

Must be signed and has to be signed can express very similar obligations. Must often presents the speaker’s conviction or authority, or a formal written rule such as a sign or regulation. Have to often points to an external requirement independent of the speaker. This is a tendency, rather than an absolute distinction.

The two are interchangeable in many everyday contexts. Speakers often choose have to as a more neutral conversational form. The distinction is most noticeable in formal wording or when a speaker explicitly emphasises insistence.

In rules of conduct, mustn’t / must not be done and can’t / cannot be done can express prohibition. Can’t also expresses impossibility: This file can’t be opened. Distinguish these from absence of obligation: doesn’t have to be done.

Doesn’t have to be done / don’t have to be done and needn’t be done express absence of obligation: doing the action is optional. Confusing this with prohibition reverses the intended message.

Use should be done and ought to be done for advice or recommendations. They can also express moral obligation or expectation, so the grammar alone does not guarantee that ignoring the recommendation has no consequences. Must / have to expresses a requirement more directly.

Ought to is less common in modern conversation, especially in negatives and questions. Should is a much more usual default; ought to can sound slightly more formal or literary.

Can be done often describes ability or general possibility: something can technically be done. Can also expresses permission: someone is allowed to perform the action.

May be done is a more formal written permission pattern in rules, notices or contracts. Could be done often describes hypothetical ability or offers a tentative suggestion, while might for permission is rare and sounds very formal or old-fashioned.

May be done, might be done and could be done can express uncertain possibility: the speaker does not know whether the action will happen. Might can sound more tentative than may, but the difference is often slight and the forms can be interchangeable; context matters.

Will be done can express a prediction, intention or promise. It does not guarantee the real outcome and can occur with probably. May, might and could present possibility more tentatively; the strength of the whole statement also depends on context.

The mechanical structure—unchanged be after a modal, choosing a past participle and ordering negatives or questions—is covered by Modal + be + past participle in the same topic. Here the form is a tool; the target is the choice of meaning.

Modal + have been + past participle evaluates a completed past action: should have been done expresses what ought to have happened; must have been done expresses a deduction. Simple could be done can also describe past possibility. Have/get something done, meaning arranging for a service, is studied separately.

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.

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.

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.

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.

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?”

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.

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.