should have / could have / would have

Rules

• Rule 1: should have → regret, criticism

  Use should have + past participle for something that was the right thing to do but didn't happen.

  Pattern: subject + should have + past participle

  Example: I should have packed a sweater. It's cold here!

  Example: You should have asked the teacher.

• Rule 2: shouldn't have → a mistake that happened

  Use shouldn't have + past participle for something that happened but was a mistake.

  Pattern: subject + shouldn't have + past participle

  Example: I shouldn't have eaten that third slice of pie.

  Example: We shouldn't have left the gate open.

• Rule 3: could have → a missed chance

  Use could have + past participle for something that was possible but didn't happen.

  Pattern: subject + could have + past participle

  Example: We could have taken the ferry, but we flew.

  Example: Be careful! You could have dropped the tray.

• Rule 4: would have → an imaginary result

  Use would have + past participle for a result that would have happened if things had been different — but didn't. We often give the reason with but.

  Pattern: subject + would have + past participle …, but …

  Example: I would have joined you, but I had a piano lesson.

  Example: The trip would have been perfect, but it rained.

• Rule 5: needn't have vs didn't need to

  needn't have + past participle → you did it, but it wasn't necessary. didn't need to + verb → it wasn't necessary (and usually you didn't do it). If we know it was done, use needn't have; if we know it wasn't, use didn't need to. Note: in American English needn't have is formal and rare; in everyday speech people usually say didn't need to / didn't have to for both.

  Pattern: needn't have + past participle · didn't need to + verb

  Example: I needn't have ironed my shirt; nobody noticed.

  Example: It was warm, so I didn't need to take a jacket.

Common mistakes

• I should have went to bed earlier. → I should have gone to bed earlier.

  have needs the past participle: go – went – gone.

• You should of told me. → You should have told me.

  should've sounds like “should of”, but it's written should have.

• She should had called. → She should have called.

  After a modal, use have with every subject, never had.