Introduction

In real communication, we often want to talk about rules, possibilities, expectations, and abilities without focusing on who performs the action. This is especially common in formal writing, public notices, academic contexts, and professional communication. The passive with modal verbs allows you to combine two powerful tools: modality (can, must, should, might, etc.) and the passive voice (be + past participle). The result is a flexible structure for describing what is allowed, required, recommended, or possible, while keeping the emphasis on the action or the object affected.

Learning Objectives

Learning Objectives
By the end of this unit, you will be able to form and use the passive with modal verbs to express ability, obligation, advice, permission, and possibility; choose appropriate modals for formal and informal contexts; avoid common errors with word order and past participles; and produce accurate passive sentences in the present, future, and perfect forms with modals.

1) Why use the passive with modal verbs?

When the agent (the doer) is unknown, obvious, unimportant, or intentionally hidden, English often prefers the passive. Add a modal verb, and you can express rules and possibilities without naming the authority or decision-maker.

Compare the focus:

Active: The manager must approve the request. (focus on the manager)
Passive: The request must be approved. (focus on the request and the rule)

Important concept
In passive sentences, the subject receives the action. With modal verbs, the structure stays stable: modal + be + past participle.

2) Core form: modal + be + past participle

The most common pattern is:

Subject + modal + be + past participle (+ by + agent)

Examples:

The report must be submitted by Friday.
This device can be repaired in under an hour.
The meeting should be postponed if the data is incomplete.
All visitors may be asked to show identification.

3) Choosing the right modal in the passive

Modal verbs keep their meanings in the passive. The difference is simply where the focus goes.

can / could (ability, possibility): The issue can be solved quickly.
must (strong obligation, necessity): Safety equipment must be worn.
should / ought to (recommendation): The instructions should be followed carefully.
may / might (permission, possibility): The application may be rejected if incomplete.
will / would (prediction, typical result, polite distance): The package will be delivered tomorrow.

4) Passive with modal perfect: modal + have been + past participle

To talk about the past (especially when judging, speculating, or reporting), use:

Subject + modal + have been + past participle

Examples:

The documents must have been signed already. (logical conclusion)
The email may have been sent to the wrong address. (possibility)
The results should have been checked before publication. (criticism/regret)

Warning
Do not use an infinitive after be in the passive. Say: “It must be done,” not “It must be do.” Also avoid double passives such as “It must be been done.”

5) Including the agent (or leaving it out)

You can add the agent with by when it matters, but many passive sentences with modals sound more natural without it.

With agent (useful when responsibility is important): The final decision must be made by the committee.
Without agent (common in notices and policies): The final decision must be made within 48 hours.

6) Common contexts and model sentences

Rules and procedures: Personal data must be protected at all times.
Customer service: Refunds can be requested within 14 days.
Academic writing: The hypothesis should be tested with a larger sample.
Workplace communication: The schedule may be changed due to operational needs.
Speculation about past events: The file might have been deleted accidentally.

Practice

Practice section
Complete each item by rewriting it in the passive with the modal given, or by choosing the correct passive form. Answers are provided in the same table.