"The door is locked. It must require a password." And "The door is locked. It must have to require a password."

3 Answers 3


The first version means: "The door is locked. I think a password is necessary to open it."

The second alternative you provide is a little awkward. The only way I think it makes sense is if you interpret it as meaning, "The door is locked. It must be mandatory for doors here to require passwords."


@Isabel Archer @LPH Yes, that's what I thought too. But then I read about the must + have to + verb (and must + have had to + verb for past) structure in an English grammar book for advanced learners, in which the writer suggests that that pattern is used when we want to conclude something based on what we know. I believe the exact examples in the book were:

"I can't access the database. You must have to put in a password. (= a password is necessary)

"Matt wasn't at home when I went round. He must have had to go out unexpectedly."

But as you said it sounds odd and it doesn't sit right with me. Which is why I started wondering how common that structure is to a native ear, if it is common at all.

  • This is not an answer; it belongs in the comments. Cheers!
    – Conrado
    May 7, 2020 at 2:10

There is no difference in the meaning. In the way of being idiomatic, only the first one is acceptable: the combination of "must" and "have to", which both are used to express necessity is pleonastic. Just "have to" is also correct.

  • It has to require a password.

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