Usage and explanation of 'Could have + V3'. How to use 'could have + V3' in a sentence.
"Could have" followed by a past participle (V3) is used to describe something that was possible in the past but did not happen. This construction is used to express missed opportunities, hypothetical situations, or possibilities that were not realized.
Usage
1. Used to state that something was possible in the past, but it didn't happen.
I could have studied more, but I went to the movies instead. (You had the ability to study more, but you chose not to.)
She could have called a taxi, but she decided to wait for the bus (Calling a taxi was an option, but she didn't do it.)
We could have gone to the beach, but it started to rain.
She could have attended the concert, but she decided to stay home.
He could have fixed the car himself, but he chose to call a mechanic.
He could have traveled to Japan last year, but he didn't have enough money.
2. Used to make a guess about something that might have happened in the past, but you're not sure.
The phone rang while I was out. It could have been my mom. (We don't know for sure who called, but it's a possibility.)
I left my keys somewhere. They could have fallen out of my pocket. (We're not sure how you lost them, but this is a possibility.)
They could have finished the project late at night, but I'm not sure.
The power went out last night. It could have been a storm, but I didn't hear any thunder.
3. Used with "if" to talk about what would have happened if things had been different in the past.
We could have won the game if we hadn't missed so many shots. (We lost the game, and missing shots is a reason why.)
If I had known it would rain, I could have brought an umbrella.
If he had studied harder, he could have passed the exam.
They could have arrived earlier if they had taken a taxi.
I could have finished the project on time if I had started earlier.
4. Used to express regret or criticize decisions or actions.
You could have warned me about the traffic.
She could have handled the situation more diplomatically.