Modals: permission and obligation

Modals: permission and obligation

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.

Look at these examples to see how can, can't, must, 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.



We often use can to ask for and give permission.

Can I sit here?
You can use my car if you like.
Can I make a suggestion?


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

Could I ask you something?
Could I interrupt?
Could I borrow your pen for a moment, please?


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

May I see your passport, please?
Customers may request a refund within a period of 30 days.
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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.

What does this sign say? Oh, we can't park here.
You can't take photos in the museum. They're really strict about it.
Sorry, we can't sell knives to under-18s.

must not/mustn't

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.

Visitors must not park in the staff car park.
Baggage must not be left unattended.
Guests must not make noise after 10 p.m.

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.


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

have to

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.

You don't have to wear a tie in our office but some people like to dress more formally.
You don't have to go to the bank to do a transfer. You can do it online.
You don't have to come with me, honestly. I'll be fine!

Do this exercise to test your grammar again.

Grammar test 2

Modals – permission and obligation: Grammar test 2

Language level

Average: 4.1 (82 votes)

Submitted by British Lesson on Mon, 13/03/2023 - 11:43


I came across with the word CAN NOT separated. Is it correct? I would like to know if the negative form of CAN is only CANNOT or we can use CAN NOT, and if so when we can use CAN NOT form? Thanks.

Hi Tony,

Thanks for your question! It should be a single word, cannot. Although people do sometimes write can not, it is an error. There is one exception - if "not" describes another verb, instead of "can", e.g. I don't mind if you don't want to go to the park. We can not go." (meaning = "we do not need to go" or "it's fine if we do not go"; "not" describes "go", not "can").

I hope that helps.


LearnEnglish team

Hi LearnEnglish team,
I would like ask about the use of "have to" in the past perfect tense. Would you please supply some examples?

Hello Rabearabea,

'I'd had to make a few calls before I could start writing' or 'She'd had to try six times before she got the car started' are a couple of examples. It's a little unusual in the past perfect, but definitely possible.

All the best,
LearnEnglish team

Thank you LearnEnglish team ( Kirk ) for your reply about the past perfect of "have to" but I came cross a strange grammatical rule in a text book of English for EFL. The rule says that the past perfect of "have to " is " have had to" ,e.g.
I have never had to go to hospital. (past perfect)
Would you please explain if this rule is correct?

Hi Rabearabea,

Sorry, that's incorrect. "Have had to" is the present perfect, not past perfect. It uses "have" as the auxiliary verb (but past perfect uses "had"). The past perfect would be --> "I had never had to go to hospital."


LearnEnglish team

Submitted by Javi Cruz on Tue, 21/02/2023 - 23:39


Hi, I have a question about how to use can't must not and musn't. We use can't , When we see any signal or rule and we can't do something, for example you must not park here, so I understand I can't park there because it's prohibited? and in the case with musn't is when I say to someone or to myself I can't or they can't do that?
With Have to or Must. We use have to when someone tell me I have to do something and must is when I think someone or myself must do something. for example: I have to do my homework because my teacher said it's very importan and with must - I must wear that dress because it's very beautiful or You must turn on the tv it's very important to watch the news

Hello Javi,

Yes, one of the uses of 'can't' is to talk about prohibitions or things that are not allowed. If I see a sign that says 'No Parking' and my friend is trying to park there, I can say to her 'You can't park here.' In this case, I'm making an observation about a rule, but I'm not making the rule myself.

It would be unusual for you to say 'You mustn't park here' in this situation because the prohibition isn't coming from you -- you're just pointing out what the rules are. It's not impossible to say it, but it would be a bit strange.

'have to' is much more commonly used than 'must', especially outside the UK. When 'must' is used, it's often a kind of self-imposed obligation and sounds almost like a reminder one gives oneself about something important. It can also be used on signs and sometimes authority figures (for example, teachers) will use it. In these cases, notice that it's the authority figure who is speaking to the person who has to follow the rules. 'have to' is more often used when we the people who have to follow the rules talk about the rules that are imposed on us.

Does that make sense? By the way, we have another set of pages on Modal verbs that you might find useful.

All the best,
LearnEnglish team