I read this sentence in a book recently:

What I should have done is given him the...

(Emphasis mine) I'm not a linguist but I thought it should be:

What I should have done is give him the...

Can anyone tell me which is right and why? Thank you.

Going by what most people have said, if the first is grammatically correct (which I do not argue), the explanation I can think of is this: from the first part of the sentence (the subject) What I should have done, there is a present perfect tense (i.e. have done). This influences the second part of the sentence (the predicate, I think that's what it is called as I'm not an English student) and makes it a present perfect tense, too (given, in this case).
Going by this reasoning, as I asked in a comment, this example should be grammatically correct:

What I did was gave him...

I'm sorry if it seems I'm pushing this too far. I'm quite particular about trivial matters.

  • That 2nd version doesn't seem grammatical.
    – F.E.
    Jun 3, 2014 at 17:58

4 Answers 4


Both sentences are grammatically correct and mean just about the same to my ear.

As Peter Shor accurately pointed out, the first one is an example of an elliptical construction and, as such, should be interpreted as follows:

What I should have done is [I should have] given him...

Consider other similar constructions:

What we have done is [we have] given the military judge the tools he or she will need to render justice.

All you have done is [you have] given me an argument to justify on anything I might wish to spendmy time on.

As for your second sentence, what I should have done is to could be an acceptable, grammatically correct alternative to it, but it's somewhat less idiomatic than the construction without to.

In addition to that, the to in there is unnecessary and doesn't add anything to the overall meaning of the sentence.

Here's a link to Google Ngram that supports my assumption.

  • 1
    Given you have said both are grammatically correct, could you add a similar breakdown of the second form?
    – Sam
    Jun 3, 2014 at 16:48

What I should have done is given him the...

I think the sentence above usually appears in informal situations including oral communication.

Recently I also read a sentence like the question above.

I look up the book PRACTICAL ENGLISH USAGE/Swan

281. infinitives (3):without to

5. after do

All I did was (to) give him a little push.

It could be helpful for those having similiar questions.


The sentence from the book is emphasizing that the person should have already given the thing to "him".

  • You are saying the first one is the right one. I'm not disputing that but I want explanations. Thank you
    – afaolek
    Jun 3, 2014 at 12:02
  • The point of the first sentence like I said was that by using "given" the writer is saying that in the past 'I' should have already given the thing to 'him'.
    – Mou某
    Jun 3, 2014 at 12:06
  • @afaolek but in your question you imply that the first might be incorrect: "Can anyone tell me which is right...?"
    – Mari-Lou A
    Jun 4, 2014 at 2:30

The first is right, as @user3306356 has identified.

A way of understanding this is to recognise that the sentence is an evolved contraction:

The 'original' full sentence would be:

What I should have done is to have given him the...

It should now be clear that "What I should have done is to have give him the..." isn't grammatical.

Edit: To clarify, as it is evidently unclear, I am not proposing my 'original' form as better, it is inferior in modern usage. I only mention it to show which sentence in the question is correct, by presenting an older BE form from which the modern form is arguably derived.

  • 1
    Your full sentence sounds ungrammatical to me. Nobody says "what I have done is to have given ...". No, they say "what I have done is I have given", and leave out the second "I have ". So I would think the original full sentence here is "what I should have done is I should have given him ...". Jun 3, 2014 at 13:21
  • It is grammatically valid, leveraging the 'should have' expression of unmet obligation to express what should have happened instead, but where what should have happened is phrased to reflect the speaker moving their perspective back through the events in question, from a point before they made the 'wrong' decision. The first sentence you write is a nonsense. In the framework I outlined the closest would be "what I have done is to give..." different meaning entirely. The should is non-trivial. Your alternative full sentence is the kind of construction a younger child might be heard to use.
    – Sam
    Jun 3, 2014 at 14:01
  • @Sam Peter is right. Nobody says, “What I should have done is to have given…”, while “What I should have done is I should have given…” is quite commonly heard from normal, adult native speakers. “What I should have done is to give…” is also perfectly grammatical, and indeed not unlikely to be heard. There is no reason the infinitive must be backshifted to a perfect infinitive—in fact, semantics would speak against doing so here. Jun 3, 2014 at 14:54
  • @JanusBahsJacquet In BE what I have suggested is not uncommon (though rare given simpler constructions such as the subject of the question). "What I should have done is I should have given..." is not considered good written BE, as it is clumsy, but is tolerable in spoken. It would usually be said without the second 'I should have'. I have not said that 'what I should have done is to give...' is ungrammatical, in fact the opposite, I outlined it as a better phrasing than the 'should...should...' Similarly the backshift is indeed unneeded, except as explanation to answer the OP.
    – Sam
    Jun 3, 2014 at 15:44
  • @Sam You are implying then that What I did was gave him ... is grammatically correct. Is that right?
    – afaolek
    Jun 4, 2014 at 6:27

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