Phrase "can't have done?"

can’'t have done?
Hi teachers,

  1. Does ‘‘can’‘t have done’’ exist in the English grammar? If it does, what does it means? Thank you…

2.They say we can use ''can and could ‘’ with verbs of percetion. But do both mean ‘‘present or past’’?

For example: I can hear you.
I could hear you. (Does it here mean present or past?)

Thank you.


‘Can’ is one of those clever little modals, literally full of potential.

Let’s imagine this conversation

A: I saw Henry this morning in the high street.

B: You can’t have done!

A: I did.

B; Well that’s strange. I thought he was on holiday in Spain

B’s first response literally means: It is not possible that you have seen Henry.

Your second point: I can hear you means I am able to hear you now. I could hear you has two possible meanings: (conditional) I could (would be able to) hear you if you spoke in a louder voice. Or: (past) I could hear you when I stood near you.


This conversation sounds very British.
In the US we would not use ‘in the high street’. (This has already been discussed in another thread.)
We’d simply say “You can’t have” (i.e. we would not use the word ‘done’) in such a context.
We also generally say that a person is ‘on vacation’.

Hi Amy,

Is it possible that in some US cities the main street is named “High Street”? I’m asking because I’ve just come across the following sentence: At ten the following morning, Clete Coley wheeled to a stop at the edge of High Street, directly in front of the Carroll Gartin Justice Building.[YSaerTTEW443543]

TOEIC short conversations: A client wants to speak to his accountant on the phone[YSaerTTEW443543]


The original question was about ‘can’t have done’ and that’s why ‘can’t have done’ is quoted in the imaginary conversation and it will be no surprise that it could as well have been ‘can’t have’ in the conversation.


Hi Torsten

There is a huge difference between a proper noun and a common noun.
The main street or streets in cities and towns in the US have a wide variety of proper names. However, I’ve never heard any American refer generically to the main street in their town as “the high street”.

The main business area in the town where I grew up is on a street called Broadway. One of the main business areas where I live now is located on Boston Post Road. Surely I don’t need to list the names of thousands of main streets in the US in order to convince you that ‘high street’ is not used as a generic term for a primary business area here.

Sorry, but in my opinion, you’re really barking up the wrong tree with this.

If you manage to discover any American who says “in the high street”, please let me know. I’d be interested in knowing where they’re from, and in what context they might actually use “in the high street”. 8)

I believe you missed the point, Alan. In the context, “You can’t have done” sounds weird to me because of the use of the word ‘done’. On this side of the pond, I’d expect to hear either “You can’t have” or possibly the longer version “You can’t have seen him.” If I were having your imaginary conversation, saying “You can’t have done” wouldn’t cross my mind as a possible third option.