The situation is where the phrase "let " is being used after "have", such that it is being used as a past participle. Such as:

I should have let her know
I should have let her known


You could have let us do yoga
You could have let us done yoga

Which is the correct usage? Are both correct? Also, what language rules does this use (i.e. Why is this the case)? I'm leaning towards using the past participle form rather than the infinitive for the verb, but I'm not sure.

If you don't have a definitive answer, I'm also interested in hearing what you think sounds more natural.

  • 1
    Believe it or not, the infinitival "know" is a non-finite clause functioning as catenative complement of "let". Although "know" is a single word, it's the head of the clause and is of course the infinitival verb-form.
    – BillJ
    Apr 15, 2016 at 19:05

1 Answer 1


I should have let her know. correct

'let' is followed by the infinitive, like Let me go.

You could have let us do yoga. correct

Note: Even though 'let' is the past participle, when followed by a verb,

it follows the rule for 'let' in the infinitive: let + inf.

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