C1 · Modal Verbs (advanced) — Lesson

Modals + perfect infinitive: past deduction

C1 deepens modal use with perfect infinitive forms (modal + have + PP) for speculation about the past, and adds continuous and passive forms.

must have + PP

She must have left — her car's gone. (logical past deduction)

can't have + PP

He can't have known — he wasn't there.

might/could have + PP

She might have forgotten the meeting.

should have + PP

You should have called me. (criticism/regret)

Past modal continuous: + have been + -ing

modal + have been + verb-ing ✓

Speculating about ongoing past

She must have been working all night — she looks exhausted.

Negative deduction

He can't have been listening — he got it all wrong.

Possible ongoing

They might have been waiting for hours.

Regretful continuous

I should have been studying instead of partying.

Modal + passive (be + PP)

Present modal passive

This must be done by Friday.

Past modal passive

It should have been completed already.

Speculation passive

She might have been told the news.

Recommendation passive

The report could be improved in several ways.

Could / would have for hypothetical past

could have + PP

She could have been a doctor. (possibility unfulfilled)

You could have asked me. (criticism — you didn't)

would have + PP

I would have helped if I'd known. (hypothetical)

She would have left by now. (typical past inference)

Common mistakes

She must have leave already.

→

She must have left already.

must have + past participle (not base verb)

He should have call me.

→

He should have called me.

past participle after have

She could of helped.

→

She could have helped.

"could of" doesn't exist — it's "could have"

Recap

Past deduction

must/can't/might have + PP

She must have left.

Past continuous

modal + have been + -ing

She must have been working.

Past passive

modal + have been + PP

should have been told

Regret/criticism

should have / could have / would have + PP

you should have called

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