Using Perfect Infinitives with Modal Verbs | English Grammar

The structure “have + past participle” is called a perfect infinitive.

In this lesson, we will learn about the combination between modal verb and perfect infinitive.

Using Perfect Infinitives with Modal Verbs




  • to refer to the past
  • to refer to unreal situations
  • to show that the activity was different from what we wanted
  • to say how confident we are that something has happened

Perfect Infinitives with Modal VerbsPin

Perfect Infinitives with Modal VerbsPin

Must + Have + Past Participle

Express deduction, a logical conclusion, probability

  • It is very cold; it must have snowed in the mountains.
  • If you can’t find your car keys, you must have left them in the house.

Can’t/Couldn’t + Have + Past Participle

Express negative deduction (impossibility in the past)

  • She can’t have passed such a difficult exam. 

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)

Perfect Infinitives with Modal VerbsPin

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 neighbours might have heard some noises when our car was stolen.

Perfect Infinitives with Modal VerbsPin

Needn’t + Have + Past Participle

Express an unnecessary action, which was, nevertheless, performed

  • needn’t have knocked at the door since, in this way, I awoke the baby. (But I knocked)
  • You needn’t have bought the flowers.

Perfect Infinitives with Modal VerbsPin

Should + Have + Past Participle

Indicate that the past obligation was not fulfilled or carried out

  •  You should have locked the door before leaving the house. (But you didn’t lock it.) 

Should + Have + Past ParticiplePin

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.)

Should + Have + Past ParticiplePin

Would + Have + Past Participle

The third conditional

  • would have gone to university if my parents had had more money. (The speaker didn’t go to university.)

Would + Have + Past ParticiplePin

Perfect Infinitives with Modal Verbs | Image

Perfect Infinitives with Modal VerbsPin

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hernan suarez
hernan suarez
5 years ago

is a excelent page ,i can learn more easy

joel koma
joel koma
3 years ago

l can now speak english with grammer due to this page.

Raj Sharma
Raj Sharma
2 years ago

You are rendering very useful tips for learners of the language. The colorful charts are so tempting. Thanks.

Maria khurshid
Maria khurshid
2 years ago

It can make learning easy

2 years ago

Could you applaud the model verb should be exercise?

1 year ago

Nice grammar

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