Future in the Past Perfect

How to build it

• Affirmative: would have + past participle: She said she would have written the letter by Friday. Short form: I’d have, she’d have.
• Negative: wouldn’t have + past participle: I knew they wouldn’t have finished by then.
• Question: usually inside a sentence about the past: I wondered if she would have left by the time I arrived.
• The same form is the third conditional (I would have helped if I’d known); context shows which one is meant.

When to use it

• Reported speech, when the original had the Future Perfect: “I’ll have finished by six,” he said → He said he would have finished by six.
• An action expected to be completed before a moment that was in the future from a past point of view: We hoped the rain would have stopped by the afternoon.

Examples

• She promised she would have read the report by Monday.
• I thought they would have left by the time we got there.
• He was sure the shop would have closed by eight.
• We knew that by the end of the year we would have saved enough money.

Common mistakes

• Keeping will have: He said he will have finished by Friday → He said he would have finished by Friday (when Friday is already past).
• Confusing it with the third conditional: I would have called you can report an earlier expectation (I’ll have called you by then → I said I would have called you by then) or describe an unreal past (I would have called you if…). When you mean an unreal past, make the if-condition clear.
• would in time clauses: She said she would have left before we would arrive → before we arrived.
• Wrong participle: would have went → would have gone.

The passive

would + have + been + V3: She said the letter would have been written by Friday. Used mostly in formal reported speech: We were told that all the tickets would have been sold by the weekend.