Modal Perfects: Should Have, Could Have, Would Have and More
Modal perfects let you talk about the past in a flexible way: what you should have done, what could have happened, and what must have been true. They are everywhere in real conversation.
By LearnLingo Team · Updated
Form
| Type | Form | Example |
|---|---|---|
| Affirmative | subject + modal + have + past participle | You should have told me. |
| Negative | subject + modal + not + have + past participle | She can't have seen us. |
| Question | Modal + subject + have + past participle? | Could he have forgotten? |
| Continuous | subject + modal + have been + -ing | They must have been sleeping. |
Have never changes to has or had after a modal. In speech have becomes a weak sound: should've, could've, would've, must've, might've. In writing, never spell it of.
| Modal perfect | Meaning | Example |
|---|---|---|
| should have, ought to have | it was a good idea, but it did not happen (regret, criticism) | I should have saved more money. |
| shouldn't have | it happened, but it was a bad idea | You shouldn't have shouted at him. |
| could have | it was possible, but it did not happen | We could have taken the train, but we drove. |
| couldn't have | it was impossible; or I am sure it did not happen | I couldn't have done it without you. |
| would have | imagined past result (often with if) | I would have called, but my phone was dead. |
| must have | I am almost sure it happened | The streets are wet. It must have rained. |
| might have, may have, could have | perhaps it happened | She might have missed the bus. |
| can't have, couldn't have | I am almost sure it did not happen | He can't have finished already. He only started at ten. |
| needn't have | it happened, but it was not necessary (mainly British) | You needn't have brought a gift. |
| How sure? | Form | Example |
|---|---|---|
| almost certain it happened | must have | You must have been tired after the trip. |
| possible | might have, may have, could have | They may have got stuck in traffic. |
| almost certain it did not happen | can't have, couldn't have | She can't have known about the surprise. |
Mustn't have is not used for deductions in standard British English; use can't have instead. In American English, must not have is possible: He must not have heard me.
How to make modal perfects
Every modal perfect has the same structure: modal verb + have + past participle. The modal (should, could, would, must, might, may, can't, needn't) stays the same for every person, and have is always have.
The past participle is the third form of the verb: gone, seen, done, taken. See the irregular verbs list when you need help. For an action in progress in the past, use have been + -ing: He must have been working late.
Because have is unstressed, it sounds like ⁄əv⁄ in speech. This is why some people wrongly write should of or could of. The correct contractions are should've, could've, would've, must've and might've; see English contractions.
You should have called me earlier.
He might not have received your email.
Could they have taken the wrong road?
She must have been waiting for hours.
Continuous form for an activity in progress.
Should have: regret and criticism
Should have + past participle means something was the right thing to do, but it did not happen. With I, it shows regret: I should have studied more. With you, he, she or they, it is criticism: You should have told me.
Shouldn't have means something happened, but it was a mistake: I shouldn't have eaten that last slice of pizza. Ought to have has the same meaning as should have but is more formal and less common, especially in American English. See should and ought to for the present forms.
Saying Oh, you shouldn't have! when you receive a gift is a polite way to say thank you; it does not really mean the person did something wrong.
I should have brought an umbrella.
You shouldn't have spent so much money on me.
They should have checked the address before they left.
We ought to have booked a table.
More formal than should have.
Could have and would have: possibilities that did not happen
Could have + past participle describes something that was possible in the past but did not happen. It can show a missed chance (We could have won if we'd played better) or a lucky escape (You could have been killed!). It can also be a mild criticism: You could have asked me first.
Couldn't have means it was impossible: I couldn't have done it without you. With a comparative, it is a strong positive: The day couldn't have been better (it was perfect).
Would have + past participle describes an imagined result, usually in the third conditional: I would have come if I'd known. It is also used on its own when the condition is clear: I would have helped you, but you didn't ask.
You could have hurt yourself!
I could have been a professional dancer, but I chose medicine.
I would have bought it, but it was too expensive.
The weather couldn't have been better.
It was perfect.
You could have told me you were going to be late.
A polite complaint.
Must have, might have and can't have: guessing about the past
We use modal perfects to make deductions: logical guesses about the past, based on evidence. Must have means I am almost sure it happened. Might have, may have and could have mean perhaps it happened. Can't have and couldn't have mean I am almost sure it did not happen.
The lights are off; they must have gone out. I can't find my keys; I might have left them at work. He can't have seen me, or he would have said hello. These are the past forms of modals of deduction.
The opposite of must have is can't have, not mustn't have. Mustn't means it is not allowed, so it is not used for guesses in British English.
You must have been so happy when you heard the news.
She might have forgotten about the meeting.
They can't have arrived yet. The plane only landed ten minutes ago.
Someone may have taken your coat by mistake.
He couldn't have stolen the money. He was with me all night.
Needn't have and didn't need to
Needn't have + past participle means someone did something, but it was not necessary. I needn't have cooked so much (I cooked a lot, but there was too much food). This form is mostly British.
Didn't need to + base verb usually means it was not necessary, so the person did not do it: I didn't need to cook (so I didn't). American English mostly uses didn't need to or didn't have to for both meanings, with context making it clear.
You needn't have waited for me. I had my key.
We didn't need to take a taxi, so we walked.
Not necessary, and we did not do it.
In real life
Modal perfects are some of the most common structures in everyday English. People use them to complain (You could have warned me!), to sympathise (That must have been awful), to apologise (I shouldn't have said that) and to wonder (Where could she have gone?).
In speech, almost everyone contracts them: should've, could've, would've, must've. Practise saying the weak sound: should've is ⁄ˈʃʊdəv⁄. That must have been hard is one of the best replies when someone tells you about a difficult experience.
You lost your passport? That must have been stressful.
Sorry, I shouldn't have said that.
Where could I have put my glasses?
You could've just told me the truth.
I would've loved to come, but I was working.
Common mistakes
I should of called you.
I should have called you.
Should've sounds like should of, but the correct written form is should have or should've.
She must have went home.
She must have gone home.
After have, use the past participle (gone), not the past simple (went).
He mustn't have seen us.
He can't have seen us.
For a strong negative guess about the past, use can't have or couldn't have. Mustn't means not allowed. American English also accepts must not have.
You should had told me.
You should have told me.
After a modal verb, always use the base form have, never had or has.
I could came to the party, but I was ill.
I could have come to the party, but I was ill.
Could + base verb talks about general ability. For a past possibility that did not happen, use could have + past participle.
Practice quiz
10 questions. Pick an answer to see if it is right and why.
1. I failed the test. I ___ harder.
2. The ground is wet. It ___ in the night.
3. He ___ the email. He wasn't at work all week.
4. Choose the correct sentence.
5. What does You shouldn't have bought me flowers! usually mean?
6. I'm not sure where Ali is. He ___ to the shop.
7. I ___ you, but I didn't have your number.
8. Why did you drive so fast? You ___ an accident!
9. You ___ so much food. Only four people came.
10. She looks exhausted. She ___ all night.
0 of 10 answered
Show all answers
- should have studied
- must have rained
- can't have read
- You could have told me.
- Thank you, that is very kind.
- might have gone
- would have called
- could have had
- needn't have cooked
- must have been working
See what the B2 English course covers, or test your level first.
People also ask
What is the difference between should have, could have and would have?+
Should have means something was a good idea but did not happen (regret or criticism). Could have means it was possible but did not happen. Would have describes an imagined result if the past had been different, often with an if clause.
Is it should of or should have?+
Always should have, or the contraction should've. Should of is a common spelling mistake because should've sounds like should of in speech.
What is the difference between must have and might have?+
Must have means you are almost sure something happened because the evidence is strong. Might have or may have means it is only one possibility.
What is the negative of must have?+
For a guess, the opposite of must have is can't have or couldn't have: He can't have known. In American English must not have is also used, but mustn't have is unusual in British English.
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