Modal verbs for expressing past probability (deduction)
|Must have, can't have, couldn't have:
expressing past probability
|Structure: modal verb + have + past participle
must have been, can't have gone, couldn't have gone, etc.
|We use must have to express that we feel sure that something was true in the past.||They must have left early.
He must have already gone.
|We use can't have or couldn't have to say that we believe something was impossible in the past.||He can't have escaped through this window – it’s too small.
She can't have said that.
She couldn't have said that.
|May / might / could have: expressing past probability|
|Structure: modal + have + past participle
may have been, could have gone, might have lost, etc.
|We use may have, could have, might have to say that it was possible that something happened in the past (but we are not 100% sure).||He may have missed the bus.
The road might have been blocked.
(= ‘I think the road was blocked, but I’m not 100% sure.’)
|The negatives are may not have and might not have. We don’t use couldn’t have in the same way.||He may not have left yet.|
I might not have given her the money; I’m not sure.
I could not have given her the money, I’m not sure.
Practise this grammar: modal verbs for past probability exercise – must have, can’t have, could have, might have (intermediate)
See also: ‘must have’ vs. ‘had to’