Should Have vs. Should Of: Which Is Correct?
Quick Answer
Should have is always correct.
Should of is always incorrect, it is a spelling error caused by the sound of should've.
Explanation
Should have is the correct grammatical structure. It is a modal perfect construction used to express regret, criticism, or advice about a past action:
The error should of occurs because in natural spoken English, should have is contracted to should've, which sounds exactly like "should of" when spoken quickly. Writers who aren't aware of this contraction mistakenly write "of" instead of "have".
The sound chain:
should have β contracted to should've β sounds like "should of"
The word "of" is a preposition. It can never follow a modal verb to form a tense.
Correct vs. Incorrect
Incorrect: You should of studied harder.
Correct: You should have studied harder.
Correct (contracted): You should've studied harder.
More Examples
The Same Rule Applies to All Modal Verbs
This error is not unique to should. It occurs with all modal verbs. The rule is the same: always use have, never of.
| Incorrect β | Correct β |
|---|---|
| should of | should have / should've |
| could of | could have / could've |
| would of | would have / would've |
| must of | must have / must've |
| might of | might have / might've |
| may of | may have |
When to Use "Should Have"
Use should have + past participle for:
1. Regret about the past
"I should have saved the document before closing it."
2. Criticizing past actions
"You should have told me about the problem sooner."
3. Advice about what was the right action
"He should have applied for the job when he had the chance."
Frequently Asked Questions
Is "should of" ever correct?
No, never. It is always a grammatical error. The word of is a preposition and cannot be used after a modal verb to form a tense. Always write should have or its contraction should've.
Why do people write "should of"?
When people speak quickly, should've sounds exactly like "should of". Writers who aren't fully aware of the contraction should've (= should have) write what they hear: "of".
Does this apply to "could of" and "would of" too?
Yes. Could of, would of, must of, and might of are all incorrect. The correct forms are could have, would have, must have, and might have.
Practice
Choose the correct word:
"We should ___ prepared better for the meeting." (of / have)