Should (Ought to) Have Done (V3)
Should have + past participle talks about past events, actions that did not happen but it would be better if they had happened. A mistake or regret is implied.
You should (ought to) have checked your report thoroughly before you handed it in.
You should (ought to) have asked my permission before you used my computer. I’m really angry with you.
We use third form (verb3) of the verb after the modal “Should / Ought to have.” (Ought to being a little stronger)
They should(Ought to) have listened to me and bought that house last year before the prices increased.
You shouldn’t have been watching TV all night yesterday, that’s why you feel so tired now.
In negative form, “Ought to” becomes “Ought not to”. Do not contract
Must Have Done (V3)
Modal “must” has a meaning of necessity, many think that “must have V3” has the same meaning as “should have V3”. However; We use must when we talk about a strong possibility based on facts referring to the past.
I saw Cynthia crying a few minutes ago. She must have heard the bad news.
I’m quite sure that I put my phone on my desk, now that it’s not there somebody must have taken it.
A: Do you know where Martin is?
B: I haven’t seen him, but I’m sure he must have left the office as it’s 5 o’clock already.
Both “must have” and “should have” are perfect modals and they should be followed by past participle (verb3)
They mustn’t have arrived (
) early, or else they would have called us.
He shouldn’t have dropped (
) out of the school. She regrets doing so now.