You must wear a seatbelt. They must

Motorcyclists have to wear a helmet.

If you’re a foreigner you have to fill in a landing card.

We use questions with ‘have to’ to ask if something is obligatory, and questions with ‘have to’ are much more common in modern English than questions with ‘must’. Here are some examples:

What time do you have to start work?

Do we have to take anything with us to the course?

Why do they have to do overtime? – Because their deadline is tomorrow.

Does he have to wear a suit to work?

Do I have to bring some form of ID?

What do we have to do now?

The negative form of ‘have to’ has a very different meaning from ‘mustn’t’. We use ‘don’t have to’ to mean something is not necessary and that there is no obligation. For example:

When you ride a bicycle you don’t have to wear a helmet, but it’s a good idea.

She doesn’t have to come to the meeting if she doesn’t want to.

We don’t have to wear uniforms to school in Italy.

I don’t have to work on Saturdays so I can do what I want.

They don’t have to read all the books the teacher recommended, just one of them.

You don’t have to pay to use the motorways in England. They are free.