I ought to help him .
I ought to have helped him.
Shall I use (have + past participle) for the past form of ought to?
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"Ought to" is a modal verb. Modal verbs have only one form. They have no -ing or -ed forms. Modal verbs are followed by the infinitive of another verb without to. The exceptions are ought to, have to and used to: You must find a job. You ought to stop smoking.
Questions are formed without do/does in the present, or did in the past. Negative sentences are formed with not or the short form -n’t and do not use do/does or did.
In case of "ought to" form the past by using "ought to have". For example: You ought to have been more careful.
"Ought to" is a semi-modal, I would say. Modal verbs (can, shall, may) have very clear past tense forms (could, should, might). "Ought to" is not nearly as clear.
I would expect "ought to" to be considered a past tense form that, like "must," has no present tense form. My reasoning is that "ought to" has the same meaning as "should," which is a past tense form. Experts (who clearly know more than I do, as linguistics is pretty far out of my area!) tend to take an opposing view and consider "ought to" to be a present-tense form. http://www.tandfonline.com/doi/abs/10.1080/00138388408598359?journalCode=nest20