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we can say : I cant' have done this
but is it possible to say : I can have done this
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"I cant' have done this" is an expression meaning "I don't believe that I have done this."

"I have done this" is not an expression to my knowledge.
Anonymous is it possible to say : I can have done this
It is possible that your native language leads you to use can in your last example. A word-for-word translation from some languages may prompt you to use can in the sentence. I wonder if you mean to say: I may have done this.

CB
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Yes, you can say like that if it is used in a question or negative sentence:

You don't think I can have done this, do you?

Do you think I can have done this?
Anonymousis it possible to say : I can have done this
No. For some strange reason, we don't use "can have X", where X is a past participle. Substitute one the following:

I could have done this. / I may have done this. / I might have done this.

CJ
Anonymouswe can say : I cant' have done this
but is it possible to say : I can have done this

No, neither are correct because the tenses are incompatible. The modal auxiliary "can" has a present time interpretation, whereas "have done" has a past time interpretion.

BillJ
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@ BillJ

I disagree. The sentence I can't have done this is correct and expresses a negative deduction about an event in the past: ' Where can I have put the remote control?' 'I can't have thrown it away.'
Echoing to others comments, I would like to and a point. As stand, "I can have done this "doesn't mean much, but if context is constructed slightly different, it is possible.

I can have this done if I want to..
I can have this done by 3 if everything goes well...
@ dimsumexpress

Hi,

But you've lost the perfect infinitive have done and changed the topic of the original question. Your sentences use the present infinitive have instead of the perfect one have done. And past participle done in your examples has nothing to do with expressing an action, or its lack, before some described time. Your exemplary sentences lack the perfective aspect. The past participle done, in your examples, is an adjectival postmodifier ot the pronoun this.
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