There was someone on Facebook who commented like this:

Next time she should of flushed the toilet.

At first, I thought he had misspelled "should have", then I was thinking that it's not correct to use should have (right?) in the future construction (I suspect 'next time' he meant to say about future). I also checked the Ngram viewer about the usage of should of and should + of + past participle (I randomly chose known).

These are the results, by the way:

The usage of should of

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The usage of should of known

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Now, my question is, does that construction exist? (I've never seen it before) If that's just a misspelling, then why is the construction used in many books (According to Ngram viewer)? What construction is it called then?

  • 7
    You ran the wrong Ngrams test. Try this comparison. Commented Sep 26, 2021 at 12:48
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    I’m voting to close this question because it's based on bad English, so no useful answer can come from it
    – gotube
    Commented Sep 27, 2021 at 3:58
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    @gotube Why does no userful answer come from it? It's a mistake that many native speakers make when writing, so it is likely to be useful to other learners who don't know which is correct. Commented Sep 27, 2021 at 10:38
  • The sentence you found is something i really really often encountered. It happenes when a german translates a sentence to english without actually translating it, meaning the sentence is just literally translated with no effords to match english grammar forms. "I had of known" is another example when a german tries to translate "I have known about this", and the all-time misused "If you will" > It might sound elegant to a native speaker cause it's basiscally correct, but the german wanted to say "If you want", because "will" is the word for wanting.
    – clockw0rk
    Commented Sep 27, 2021 at 13:28
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    @clockw0rk Sorry, but that's just bollocks. The idiom "if you will" certainly does not come from German speakers incorrectly translating to English, rather the English auxiliary "will" and the German verb ultimately come from the same root, and it still has retained some of its old meaning. Also, I cannot think of a way a German could (literally) translate "Ich habe das gewusst / I have known about this" to "I had of known". Word for word, it's more like "I have that known".
    – neondrop
    Commented Sep 27, 2021 at 13:46

4 Answers 4


Why does that construction exist?

Because in spoken language, should have and should of are indistinguishable (when enunciated as contracted should've). And some native speakers are so ignorant they don't understand that basic syntax requires an auxiliary verb after should, not a preposition.

But note that some perfectly competent Anglophones may deliberately write the incorrect version sometimes as a facetious usage. OP's cited Facebook poster probably isn't very competent, given that "next time" is future, so the auxiliary have (part of a "Present Perfect = Past" verb form) shouldn't be there anyway. But even people who know perfectly well that it's "incorrect" sometimes write things like a whole 'nother ballgame for much the same reason.

I don't know why OP wrote it's not correct to use should have. That's exactly what the Facebook writer should of1 written!

1 In case it's not obvious, that's me being facetious! But actually whereas one should've = should have done something in the past, when talking about a future "next time" it's what one should do (infinitive do, not have + Past Participle done).

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    "some native speakers are so ignorant they don't understand that basic syntax requires an auxiliary verb after should, not a preposition." - this. Also you see could of, would of, might of, etc. I recently saw 'ought to of' in a colleague's email, and he was not junior or young. Commented Sep 26, 2021 at 12:00
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    I think it's actually the contraction "should've" that's indistinguishable, which is almost universally used when it's used as an auxiliary verb phrase. It doesn't apply when "have" is the main verb itself. @MichaelHardy
    – Barmar
    Commented Sep 26, 2021 at 20:17
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    "I don't know why OP wrote it's not correct to use should have." As they wrote in their question, user516076 thinks it's not correct because "next time" refers to the future but "should have" refers to the past. After "should of" is corrected to "should have", I agree with user516076 that the quote "Next time she should have flushed the toilet" sounds odd to me. I would instead say either "Next time she should flush the toilet" (future) or "She should have flushed the toilet" (past).
    – Bavi_H
    Commented Sep 26, 2021 at 23:36
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    Most native speakers don't give two hoots about rules of syntax, auxiliary verbs, etc, all of which are concepts created by linguists to describe what people actually say. I'm not saying "should of" should be considered "correct" rather than "a common mistake", but the level of snooty condescension in this answer is well over the top.
    – IMSoP
    Commented Sep 27, 2021 at 14:46
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    @FumbleFingers Again, my objection was not to calling it incorrect, but using condescending language like "so ignorant" and "perfectly competent", which serve no purpose other than to make you feel superior.
    – IMSoP
    Commented Sep 27, 2021 at 16:33

"Should of" is a misspelling of "should've"; "should've" is pronounced the same as (or very close to) "should of". It is indeed incorrect to use "should've" for future event. It should be just "Next time, she should flush the toilet."

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    Maybe this is not about future events. Contrast "Next time, she should flush the toilets." and "The next time she should have flushed the toilets, she discovered that there was no water in the tank."
    – Stef
    Commented Sep 27, 2021 at 12:56
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    @Stef The context is given in the question, and doesn't match that interpretation.
    – IMSoP
    Commented Sep 27, 2021 at 14:43
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    @IMSoP The only context I see in the question is "There was someone on Facebook who commented". I don't see how you jump from that meagre piece of information to "it was not in the past".
    – Stef
    Commented Sep 27, 2021 at 16:02
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    @Stef The quote is given as a complete sentence. There's no way to fit your convoluted conditional clause around the quote.
    – IMSoP
    Commented Sep 27, 2021 at 16:34
  • The quote given makes no sense for two reasons, it uses "should of", and it refers to a future event in the past tense. Salvaging useful meaning from it is difficult. Commented Sep 28, 2021 at 1:52

Using "should of" when "should have" would be correct standard English grammar is a common usage. In some cases this occurs from hearing "should've" (intended as short for "should have") as "should of" because there is little if any difference in sound. But I think (although I cannot prove) that this use of "should of" is also a common, and so arguably "correct", use in certain English dialects.


  • I should have known better.Green Check
  • I should of known better.Red X

Using "should have" for a future event, instead of just "should" is also incorrect, but is also not uncommon among fluent speakers. I suspect it comes from mentally placing oneself after the future event has occurred, and then looking back on it. Or it may just be that correction of a past event is so much more common that the "should have" form leaps to the mind, even when it is not correct. This is supported by the use of a past tense form of "flush" in the example.

In any case, the fully correct version dealing with an anticipated future event would be:

Next time, she should flush the toilet.

In this form the issue of "of" vs "have" goes away, because neither is needed or wanted.


There is only one way "should + of" phrasing can be used:

He should, of course, have used correct grammar on his college application.

  • -1 too absolutist, and ignoring dialect. Commented Sep 29, 2021 at 14:48

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