would have had to have been v. would have had to be

This is how I understand it now...

Let's reduce the sentence to the simple present.

  • The benefit must be paid before 1 May 2010.

This is the same as:

  • The benefit has to be paid before 1 May 2010.

Notice the infinitive after "has": "to be". It is sometimes possible to use a construction called the "perfect infinitive".

  • The benefit has to have been paid before 1 May 2010.

This sentence sounds OK to me, but it sounds unnecessary to use this construction. It seems to me that you can just use the infinitive rather than the perfect infinitive.

So the question is: why must you use the perfect infinitive? I'm finding it difficult to find any explanation online of when you use this exactly. I've found this. It can be used when referring to things in the past or future.

However, the important point in this particular sentence is that "have to have known" is the same as "must have known". These are both used in the sense of "probably know". "He has to have known" = He probably knew.

  • The benefit had to have been paid before 1 May. = The benefit was probably paid before 1 May.

OK, now turning to the "had".

Adding "would have" to a verb changes it so that it refers to something hypothetical in the past, i.e. something that didn't happen in the past. Example: "I would have gone to Spain with them but I caught a cold."

So saying "the benefit would have had" instead of "the benefit had" means there was no past obligation regarding the benefit. It's discussing something hypothetical in the past.

So I think this sentence is possible:

  • 2.The benefit would have had to have been paid before 1 May.

It's referring to a hypothetical past probability.

/r/grammar Thread Parent