Modals of Deduction in the Past

• When we look at past clues in business and make logical guesses about what happened, we use past modal verbs. We form them with modal + have + past participle.
• Modal
• Meaning
• Example
• must have
• almost certain it happened
• Nexus Corp must have received a better offer from London.
• might have / could have
• possible it happened
• David might have forgotten about the account review.
• can't have / couldn't have
• almost certain it didn't happen
• They couldn't have left without talking to us first.
• Remember
• Use must have when evidence strongly supports a past action.
• Use might have or could have for things that were possible in the past.
• Use can't have or couldn't have when something was logically impossible.
• Always follow the modal with 'have' and a past participle.
• Examples
• Our key client must have gone to the rival firm in Chicago.
• Sarah might have missed our email about the price changes.
• They can't have checked their bank statement before calling us.
• Common mistakes
• They must left the office early yesterday.
• They must have left the office early yesterday.
• She can't saw the message on her phone.
• She can't have seen the message on her phone.

Complete the sentences

• Brian (forget) ____ to send the invoice to Seattle.
• The competitor (undercut) ____ our prices in New York.
• They (receive) ____ our warning sign about the delay.
• Mark (lose) ____ the key client's folder in Boston.
• Management (notice) ____ the drop in customer loyalty.
• She (know) ____ about the new suppliers in Austin.

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