Exceptions for Conditional Sentences

So far you have only learned the basic rules for Conditional Sentences. It depends on the context, however, which tense to use. So sometimes it's possible for example that in an IF Clause Type I another tense than Simple Present is used, e.g. Present Progressive or Present Perfect.

Conditional Sentences Type I (likely)

Condition refers to: IF Clause Main Clause
future action Simple Present If the book is interesting, … Future I …I will buy it.
Imperative …buy it.
Modal Auxiliary …you can buy it.
action going on now Present Progressive If he is snoring, … Future I …I will wake him up.
Imperative …wake him up.
Modal Auxiliary …you can wake him up.
finished action Present Perfect If he has moved into his new flat, … Future I …we will visit him.
Imperative …visit him.
Modal Auxiliary …we can visit him.
improbable action should + Infinitive If she should win this race, … Future I …I will congratulate her.
Imperative …congratulate her.
Modal Auxiliary …we can congratulate her.
present facts Simple Present If he gets what he wants, … Simple Present …he is very nice.

Conditional Sentences Type II (unlikely)

Condition refers to: IF Clause Main Clause
present / future event Simple Past If I had a lot of money, … Conditional I …I would travel around the world.
consequence in the past Simple Past If I knew him, … Conditional II …I would have said hello.

Conditional Sentences Type III (impossible)

Condition refers to: IF Clause Main Clause
present Past Perfect If I had known it, … Conditional I …I would not be here now.
past Past Perfect If he had learned for the test, … Conditional II …he would not have failed it.