Ought to

The use of ought to is similar to should, but it is much less frequent.Like should, the verb ought to does not have a past form. It is only used with reference to the present and the future.Ought to is rarely used in questions and negatives. When it is, it is confined mainly to formal styles.In negatives, not comes between ought and to. In questions, the subject comes between ought and to.

I ought not to have said those things to her.
Ought we to make such a sacrifice for the benefit of future generations?

Ought to is used as follows:

to express an obligation or an expectation that someone should do something.

You ought to listen carefully.
We ought to leave now.
Lucy ought to go by herself.
People ought to be a bit nicer to us.

to express the likelihood of something happening.

Annabel ought to be here by now.
The journey ought to take about 2 hours.

Ought to + have + past participle of main verb is used to express regret that something was not done or to reproach someone for doing or not doing something.

I ought to have spoken up earlier. I’m sorry.
You ought to have offered to help.
They ought to have told us what to expect.

In questions and negatives, should is frequently used instead of ought to because it sounds more natural.

Ought I to report it to someone in authority?
Should I report it to someone in authority?
Ought we to make a start?
Should we make a start?

ought to
The contracted negative form is:	oughtn’t (to).

Oh dear, we oughtn’t to have let that happen.
Well then she ought to do something about it, oughtn’t she?