Should with perfect infinitive

Should can be used with the perfect infinitive (have + past participle). This structure has several meanings.

Should have + past participle

This structure is used to talk about past events which did not happen.

  • I should have posted that letter yesterday itself, but I forgot.
  • She should have knocked at the door before entering the room. (It was necessary but she didn’t do it.)
  • They should have informed his parents that he was unwell. (They didn’t inform his parents.)
  • He should have worked harder. (He didn’t work harder.)
  • She should have made another attempt before quitting.
  • He should have obtained the necessary permissions before opening the shop.

This structure can also be used to talk about logical possibility.

  • 10 o’clock – he should have reached home.
  • They should have received our letter.

In most cases, the actual meaning of this structure can be inferred using context.

Should not have + past participle

This structure is used to talk about unwanted things that happened.

  • You shouldn’t have said things like that to her – it really upset her.
  • She shouldn’t have refused that job offer. (= She refused it but it was totally unnecessary.)
  • He shouldn’t have invested all his money in stocks. (= He invested all his money in stocks, but that was a stupid thing to do.)
  • They shouldn’t have bought that used car. (= They bought that used car, but it was not a wise decision.)
  • We shouldn’t have waited for his approval. (= We waited for his approval, but that was not necessary.)