Why do people write 'could of' instead of 'could have'?

Which is correct: "Could have" — always. "Could of" is an error.

Why people write "could of": In spoken English, "could have" contracts to "could've" (sounds like "could-uv"). When people write what they hear, they write "could of" — because "of" sounds like "uv."

This is called an eggcorn — a word or phrase misheard and reinterpreted as something that sounds similar.

• "Should of" → should have (should've)
• "Would of" → would have (would've)
• "Must of" → must have (must've)

How to spot the error: "Could" is a modal verb. Modal verbs are always followed by a base verb ("have"), never a preposition ("of"). Ask: does "of have" make sense? No. "Have" always follows.

In formal writing: Always write "could have." "Could of" is considered a grammatical error.

Tags: grammar, common mistakes, writing, modal verbs