1. How they are formed
could have + V3 should have + V3 might have + V3
These forms describe unrealized past possibilities, advice, or assumptions.
Rule details
B1 (Intermediate)
could have + V3 should have + V3 might have + V3
These forms describe unrealized past possibilities, advice, or assumptions.
Could have:
I could have gone to the party, but I stayed home.
Should have:
You should have called me earlier.
Might have:
She might have missed the train.
Could have vs Might have
Could have often implies ability/possibility; might have stresses uncertainty.
Should have
Used when someone did not do what was expected or advisable.