The present subjunctive has the same form as the infinitive without to for all persons, including third person singular. It is used:

This topic is discussed in details on the page Tense changes in indirect speech.

When reporting structureThe way in which the parts of a sentence, clause or expression are arranged. E.g.: make somebody + infinitive in "The teacher made me rewrite the composition."s such as wish, would rather, it's (high) time etc., the same rules apply as in the case of reporting second and third conditional sentences.

When reporting a third conditional, we apply no tenseA grammatical category that is marked by verb inflection. To express when an event or action happens in time or when a state exists, we use tenses. changes.

"If they had been more careful, they wouldn't have been killed in the accident", the policeman muttered.
The policeman remarked that they wouldn't have been killed in the accident if they had been more careful.

When reporting a second conditional, the following tenseA grammatical category that is marked by verb inflection. To express when an event or action happens in time or when a state exists, we use tenses. changes may be applied.

When reporting a first conditional, the following tenseA grammatical category that is marked by verb inflection. To express when an event or action happens in time or when a state exists, we use tenses. changes may be applied.

When reporting a zero conditional, the following tenseA grammatical category that is marked by verb inflection. To express when an event or action happens in time or when a state exists, we use tenses. changes may be applied.

The rules that apply here are essentially the same as those discussed on the previous pages, that is, tenseA grammatical category that is marked by verb inflection. To express when an event or action happens in time or when a state exists, we use tenses. and modal changes occur if the reported sentence is out of date at the timeA concept which is related to our perception of reality; that part of existence which is measured in seconds, minutes, hours, days, weeks, etc. of reporting. Note that, even in this case, some tenses and modals do not change.

Reporting verbA part of speech that expresses an action or a state. E.g.: John seldom plays tennis.s expressing opinion

In case of reporting verbs expressing opinion (assume, expect, suppose, think etc.) usually it is the main clauseA clause that could be a sentence in itself. E.g.: I wouldn’t go there if I were you. ("I wouldn't go there") When I arrived he was surfing. ("he was surfing") that is negated.

advise, agree, demand, insist, prefer, propose, recommend, request, suggest, urge etc.