Modal verbs (can, must, should, may, will…) also have a passive: modal + be + past participle. It is common in rules, instructions, signs and formal writing, where the doer is not important.
Form
| Structure | Example |
|---|---|
| modal + be + past participle | It must be done today. |
| modal + not + be + past participle | It can't be changed. |
| modal + have been + past participle (past) | It should have been finished. |
When to use it
- Rules: Visitors must be accompanied.
- Possibility: The match could be cancelled.
- Advice and obligation: The form should be signed.
- The past: modal + have been + participle: The mistake could have been avoided.
Examples
- The work must be finished today.
- This can be done easily.
- The door should be locked at night.
- Children mustn't be left alone.
- The problem could have been avoided.
- Passports may be checked at the gate.
Common mistakes
- Missing “be”: It must done → It must be done.
- The base verb: It can be do → It can be done.
- A past passive without “have”: It should been done → It should have been done.