The structure “have + past participle” is called a perfect infinitive.
Learn how to use perfect infinitive with modal verbs in English: must have, can’t have, should have, shouldn’t have, needn’t have, ought to have, may have, might have, could have, would have.
You can jump to any section of this lesson:
- 1 Using Perfect Infinitives
- 1.1 Must Have + Past Participle
- 1.2 Can’t Have + Past Participle
- 1.3 Should Have + Past Participle
- 1.4 Shouldn’t Have + Past Participle
- 1.5 Needn’t Have + Past Participle
- 1.6 Ought to Have + Past Participle
- 1.7 May Have + Past Participle
- 1.8 Might Have + Past Participle
- 1.9 Could Have + Past Participle
- 1.10 Would Have + Past Participle
- 2 Perfect Infinitive with Modal Verbs | Picture
- 3 Perfect Infinitive with Modal Verbs | Video
Using Perfect Infinitives
Must Have + Past Participle
Express a deduction about something that has happened. We feel quite sure about it.
I didn’t hear her voice . She must have gone out.
It is very cold; it must have snowed in the mountains.
Can’t Have + Past Participle
Describe a deduction about something that didn’t happen in the past based on present evidence.
He can’t have fallen in love with her. She’s married.
She can’t have passed such a difficult exam.
Should Have + Past Participle
Express the idea that something was desirable or needed but didn’t take place.
She should have asked you before borrowing your pen.
You should have locked the door before leaving the house. (But you didn’t lock it.)
Shouldn’t Have + Past Participle
Something took place but it wasn’t desirable.
She shouldn’t have taken the matter too seriously.
Needn’t Have + Past Participle
Express that something was done but it wasn’t necessary. The person who did it thought it was necessary.
When the party was over, I realized that you needn’t have cooked so much food as most of it was untouched.
I needn’t have knocked at the door since, in this way, I awoke the baby. (but I knocked)
Ought to Have + Past Participle
Express an unfulfilled duty or obligation.
Paul ought to have waited until the lights were green before he crossed the street. (But he didn’t wait.)
May Have + Past Participle
Express the possibility that an action took place in the past.
The little girl may have lost the key. (It is possible that she lost the key.)
Might Have + Past Participle
Express a past possibility.
Our neighbors might have heard some noises when our car was stolen.
Could Have + Past Participle
Express past reference about something that was not carried out.
You could have done it. (You didn’t do it)
She could have called the doctor early in the morning. (She didn’t call the doctor)
Would Have + Past Participle
Used in the Third Conditional.
I would have gone to university if my parents had had more money. (The speaker didn’t go to university.)