Advanced Modal Verbs: Past and Probability

Modals about the past and about probability: modal + have + V3.

Certainty now

• must — almost sure: She's late. She must be stuck in traffic.
• might / may / could — possible: He might be at home.
• can't — almost impossible: That can't be true. (not mustn't in this meaning)

The past

• must have: He must have forgotten.
• might have / may have / could have: She might have missed the bus.
• can't have / couldn't have: He can't have seen us. He was in London.
• should have — regret / expectation: You should have called.
• could have — a missed possibility: We could have won.