Future Perfect Simple – Rules

The future perfect simple tense refers to a completed action in the future. When we use this tense we are projecting ourselves forward into the future and looking back at an action that will be completed some time later than now. It is most often used with a time expression.

We use the future perfect simple when we assume that an action will have happened by some time in the future – it will happen between now and some point in the future.

Ann will have finished the report by Wednesday.
(She may finish it earlier than on Wednesday.)
They will have begun the meeting by the time we arrive.
(When we arrive, we will be late.)

The future perfect simple tense may also be used to express the completion of an action before another activity in the future.

Tom will have left before the office closes.