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Which one to use?Advancedmodal verbmodal verb
Should havevsCould have / Would have
'Should have' expresses a past obligation not fulfilled; 'could have' expresses past capacity or possibility not acted upon.
Side-by-side comparison
Should have
modal verb"Should have + past participle" expresses that something was the right or advisable thing to do in the past but it did not happen. It implies regret or criticism.
You should have told me you were not coming. I waited outside for a whole hour.
She should have checked the opening hours before going, it was completely closed.
They should have left earlier to avoid getting stuck in the rush hour traffic.
Could have / Would have
modal verb"Shouldn't have + past participle" expresses the opposite: something should not have been done but was. It also implies regret or disapproval.
If I had studied more, I could have passed the exam easily.
She would have come to the party, but she was feeling unwell that evening.
He could have taken a taxi but decided to walk home instead.
Common mistake
Two critical errors:
- 1."I should of done it" is wrong: "should've" comes from "should HAVE," never "should of" (same with "could of" and "would of").
- 2.Second error: confusing "should have" (obligation not met, criticism) with "could have" (possibility not realized, neutral) with "would have" (hypothetical result of an unmet condition).
Trick to remember it
- •Semantic key: "should have" = "it was the right thing, but it did not happen" (unmet obligation).
- •"Could have" = "it was possible, but it did not happen" (neutral).
- •"Would have" = "it would have been the result if the condition had been met" (past hypothesis).
- •Never "of", always "have."
Quick rule
- •"Should have" = obligation or expectation not met (criticism/regret).
- •"Could have" = possibility not realized (neutral).
- •"Would have" = hypothetical result of a past conditional.
- •Never "should/could/would of", always "have."
Did you know?
The error of writing "should of" instead of "should have" is one of the most frequent spelling errors among native English speakers, especially in informal written English. The reason is strictly phonetic: "should've" sounds identical to "should of" in fluent speech. The result is that native speakers who pronounce English perfectly misspell it because their spelling memory is mapped onto their phonetic representation. This phenomenon, a spelling error caused by the phonetic identity of two forms, is called "homophonic merger." Other classic examples in English: "your/you're," "there/their/they're," "to/too/two."
Practise what you learned
Exercise 1 · Pick the right one
You _____ have told me earlier! Now it's too late to change the plans.
Exercise 2 · Pick the right one
She _____ have arrived by now. The flight landed an hour ago.
Exercise 3 · Form the word
Related word pairs
Could ofvsCould have
'Could of' does not exist in correct English; the correct form is always 'could have' (could've).
Second conditionalvsThird conditional
The second conditional expresses imaginary present or future situations; the third expresses past situations that did not happen.
WishvsIf only
'Wish' and 'if only' express desires about hypothetical situations; 'if only' is more emphatic and dramatic.
AvsAn
'A' is used before consonant sounds; 'an' is used before vowel sounds.
Bryan López
Founder of SpeakUP Academy