<h1>should have</h1>

Advisability/necessity: the perfect and past: “should have”

The structure “should have” it is used in order to express whatever is desirable or necessary, but did not happen. Through this structure, we may be expressing:

- Failure to respect a prohibition:

You should have obeyed the agent. ( but you didn’t )

You shouldn’t have stopped out of the kerb ( but you did )

- Criticism:

You should have called your sister in law for her birthday. ( but you didn’t )

You shouldn’t have paid the restaurant’s bill in advance. ( but you did ).

This structure contrasts with “had to be + past participle “where we express something necessary or desirable and did happen.

For example in these examples in the passive form:  

-Should have been sent quickly

-Had to be sent quickly.

The first one means it was desirable to send quickly, but it wasn’t sent quickly.

In the second, nevertheless, it was necessary to be send quickly and it was sent quickly.

Finally, we have “had to” that express an action performed in the past because this was necessary and there was no choice:

I had to catch a taxi to be at the office on time.