• Perfect Modals: Could Have

• 
• Use the perfect modal form of could to show ability*  or possibility** about actions/events in the past.

  
  

  subject + could + have + past participle

  
  

  -I could have studied more for the exam.  It was really hard!

  (This shows ability because the person has the skill to study more if they want.)
  

  
  

  -I could have gone to Yale University, but it was too expensive.

  (This shows possibility because Yale University was an option the person did not choose.)

• I could have woken up earlier to go through my notes one more time. You could have had more fun during our sophomore year. She could have bought  the book, but she borrowed it from her professor.

• *Ability: the skill to do something
  **Possibility: something you can choose from different options

Source : Alison