Have to and Must

Have to: Obligation and Necessity

I have to do something means it is necessary to do it, I am obliged to do it.

• You can’t turn right here. You have to turn left.
• I have to wear glasses for reading.
• He has to work late tonight, so he can’t join the team dinner.
• Last week the server crashed and we had to restore the backup manually.
• I haven’t had to file a support ticket for ages.

Questions and Negatives with Have to

Use do / does / did in questions and negative sentences (present and past simple):

Form	Example
Present question	What do I have to do to get a new badge? (not What have I to do?)
Present negative	Karen doesn’t have to work Saturdays. (not Karen hasn’t to)
Past question	”Did you have to wait long for the client?” “No, only ten minutes.”

Have to with Other Verb Forms

You can say I’ll have to …, I’m going to have to …, I might have to …, I may have to …:

• They can’t repair my laptop, so I’ll have to get a new one. (or I’m going to have to get a new one.)
• We might have to change our plans for the product launch. (or We may have to change …)

Must: Personal Opinion and Recommendations

Must is similar to have to. You can use either when you give your own opinion about what is necessary, or when you recommend something:

• I haven’t spoken to the new hire for ages. I must phone her. / I have to phone her. (= I say this is necessary)
• Mark is a really helpful colleague. You must meet him. / You have to meet him. (= I recommend this)

Have to for Facts vs. Must for Rules

Use have to (not usually must) to say what someone is obliged to do as a fact, not as the speaker’s opinion:

• I have to work from 8:30 to 5:30 every day. (a fact about my schedule)
• Jane has to travel a lot for her work.

Use must in written rules and instructions:

• Applications for the position must be received by 18 May.
• Safety helmets must be worn on the construction site.

The Past: Had to

Use had to (not must) for the past:

• I went to the meeting yesterday, but I had to leave early. (not I must leave early)

Mustn’t vs. Don’t Have to

Mustn’t and don’t have to are completely different.

	Meaning	Example
mustn’t	Don’t do it. It is prohibited.	This report is confidential. You mustn’t share it with anyone.
mustn’t		I promised I’d be on time. I mustn’t be late.
don’t have to	You don’t need to do it (but you can if you want).	You don’t have to attend the meeting. I can go alone.
don’t have to		I don’t have to be at the presentation, but I’m going anyway.

Have Got to

You can use have got to instead of have to:

• I’ve got to finish this report tomorrow. = I have to finish this report tomorrow.
• When has Helen got to leave? = When does Helen have to leave?

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