Grammar Reference

Unit 5 - ‘Have to’ and ‘must’ (obligation)

Meaning and use

If you have to do something, it is necessary for you to do it. It’s a law, an obligation or a fact.

You have to get a visa if you want to go to Russia.
According to our agreement, we have to send these orders to our client today.
I have to go to the doctor later today.


If you must do something, it is necessary for you to do it, but this is often your opinion or a rule that you have made yourself.

I must remember to buy a birthday card for Alice today.


We see must (not have to) in formal written notices or rules that an organization has made itself.

All students must be at the examination hall fifteen minutes before the exam.


We can often use either have to or must in a sentence. But be careful! There a big difference in meaning between don’t have to and mustn’t.If you don’t have to do something, it isn’t necessary to do it, but you can if you want.

You don’t have to finish the spreadsheet today. Tomorrow will be fine.


If you mustn’t do something, it means ‘don’t do it’. It is necessary not to do it.

Employees mustn’t send passwords by email.


I mustn’t make any mistakes this time.



We use have to / must + infinitive without ‘to’. Must is the same form for all persons (I, you, he, she, etc.). Have to changes to has to in the third person singular (he, she, it).

Karen has to get up at six every day in order to get to work on time.


You must drive more carefully or you will have an accident.


You don’t have to take a towel. The swimming pool provides them.
They’re expecting us to call so we mustn’t forget.

It is possible to ask questions with Must + subject...? but it is much more common to use Do/Does + subject + have to...?

Do I have to come
to the meeting tomorrow? (Must I come to the meeting tomorrow?)


Take note: the future and the past

There is no future or past form of must. We use will have to (future)and had to (past).

It’s too late now. You’ll have to talk toher tomorrow.
All the trains were cancelled, so we had to get a taxi.
Did you have to write it all again?

Take note: have got to

In informal British English, we sometimes use have got to instead of have to. They mean the same.

You’ve got to get a visa if you want to go to Russia.


Have we got to send these orders today?


Spoken English

Have to and must are modal verbs. When we say modal verbs, we usually say them quickly and often without emphasis. So have to sounds like ‘hafta’(haf tə). Must sounds like ‘mus’ (məs). You don’t hear the final /t/ sound in must.