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Look at these examples to see how , can't, , mustn't, have to and don't have to are used.

You can put your shoes and coat over there.
You can't leave your bike there.
I must call the electrician and get that light fixed.
You mustn't worry about me. I'll be fine.
You have to have a licence to drive a car.
You don't have to have a licence to cycle on the roads.

Try this exercise to test your grammar.

Grammar test 1

Modals - permission and obligation: Grammar test 1

Read the explanation to learn more.

Grammar explanation

We often use verbs with modal meanings to talk about permission and obligation.

Permission

We often use can to ask for and give permission.

We also use could to ask for permission (but not to give it). Could is more formal and polite than can.

May is the most formal way to ask for and give permission.

Prohibition

We use can't and mustn't to show that something is prohibited - it is not allowed.

We use can't to talk about something that is against the rules, particularly when we didn't make the rules.

We use must not to talk about what is not permitted. It is common on public signs and notices informing people of rules and laws.

We use mustn't particularly when the prohibition comes from the speaker.

(Parent to child) You mustn't say things like that to your sister.
(Teacher to student) You mustn't be late to class.
I mustn't let that happen again.

Obligation

We use have to and must to express obligation. There is a slight difference between the way we use them.

Have to shows us that the obligation comes from outside the speaker.

We have to wear a uniform when we're working in reception.
(Student to teacher) When do we have to hand in our homework?
Al has to work tomorrow so he can't come.

We sometimes call this 'external obligation'.

Must expresses a strong obligation or necessity. It often shows us that the obligation comes from the speaker (or the authority that wrote the sentence).

I must phone my dad. It's his birthday today.
(Teacher to student) You must hand in your homework on Tuesday or you will lose ten per cent of your mark.
(Sign on a plane) Seat belts must be worn by all passengers.

Note that we don't use must to express obligation in the past. We use have to instead.

I had to pay £85 to renew my passport last week.

No obligation

don't have to

We use don't have to to show that there is no obligation. You can do something if you want to but it's not compulsory.

Do this exercise to test your grammar again.

Grammar test 2

Modals - permission and obligation: Grammar test 2

Language level

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Do you know how to use modal verbs to talk about permission and obligation? Test what you know with interactive exercises and read the explanation to help you.

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Only to 24/04/2020

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