In standard English it is generally treated as a full modal verb, lacking an infinitive, present participle and past participle, with the exception that it catenates with a to-infinitive rather than a bare infinitive: The question tag form is without to; e.g. "ought you?" or "oughtn't you?".
However in non-standard English the "to" can be dropped.
|Positive||You ought to do something||You ought to have done something|
|Question||Ought you to do something?||Ought you to have done something?|