No le pagaré aunque haga su trabajo: I shall not pay him although he may do his work.
The above rules have liberties and exceptions to be learnt by practice, generally turning on whether the action is intended to be alluded to =as a fact= or as =a mere conception=.
V. The Subjunctive Mood is used after cuando, así como, luego que and similar expressions when the action of the verb refers =to the future=, as—
Lo haré cuando tenga tiempo: I shall do it when I have time.
N.B.—The Future Subjunctive is often used in this case.
VI. The Subjunctive Mood is used after si (conditional if) when the context requires the following verb in the past form, as—
Lo haría si tuviese (tuviera) dinero: I should do it if I had money.
N.B.—If the context requires the verb in the present form, the
Indicative Present must be used, as—
Lo hago si tengo tiempo: I do it if I have time.
Lo haré si tengo tiempo: I shall do it if I have time.