Modals: permission and obligation
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
Read the explanation to learn more.
Grammar explanation
We often use verbs with modal meanings to talk about permission and obligation.
Permission
can
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?
could
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
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.
These pages may be photocopied for classroom use.
Prohibition
We use can't and mustn't to show that something is prohibited – it is not allowed.
can't
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.
Obligation
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
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
Dear teacher, can we use “don’t ban” or doesn’t ban”? Because I can’t find any information about the negative form of the verb “ban”.
Maybe does it mean prohibit so we can’t have the negative form?
Many thanks.
Hello KatherineThu,
It's perfectly fine to use a negative form with the verb ban or prohibit. For example:
Peter
The LearnEnglish Team
Hello,
Regarding verbs of obligation, could you please explain the difference between 'to have to' and 'to need to'?
Thank you
Hello User_1,
Both forms describe an obligation. The difference between them is very subtle and in many contexts both are possible.
Have to is more common when the obligation is external and comes from some kind of rule, regulation or expectation. Need to is more common when an action is necessary in order to achieve some other goal. However, as I said, in many contexts the speaker can choose freely between them as it's really a question of how the speaker sees the situation rather than any objective, factual distinction.
Peter
The LearnEnglish Team
Hello Peter,
Thanks for your explanation.
1- A child to his father:
𝘶𝘴𝘶𝘢𝘭𝘭𝘺 “𝘊𝘢𝘯 𝘐…?” (𝘤𝘢𝘴𝘶𝘢𝘭, 𝘧𝘢𝘮𝘪𝘭𝘪𝘢𝘳):
-𝐂𝐚𝐧 I go outside, Dad?
2-A student to his teacher:
𝘰𝘧𝘵𝘦𝘯 “𝘊𝘰𝘶𝘭𝘥 𝘐…?” (𝘮𝘰𝘳𝘦 𝘱𝘰𝘭𝘪𝘵𝘦, 𝘳𝘦𝘴𝘱𝘦𝘤𝘵𝘧𝘶𝘭):
- Could you say the question again, please?
3-Seller to a customer:
𝘐𝘯𝘴𝘵𝘦𝘢𝘥 𝘰𝘧 𝘮𝘢𝘬𝘪𝘯𝘨 𝘪𝘵 𝘢 𝘳𝘦𝘲𝘶𝘦𝘴𝘵, “𝘮𝘢𝘺” 𝘸𝘰𝘳𝘬𝘴 𝘣𝘦𝘴𝘵 𝘢𝘴 𝘢 𝘸𝘪𝘴𝘩 𝘰𝘳 𝘱𝘰𝘭𝘪𝘵𝘦 𝘣𝘭𝘦𝘴𝘴𝘪𝘯𝘨:
-Thank you for your visit! 𝙈𝙖𝙮 your feedback help us improve and serve you better.
4-Teacher to students:
a-𝙻𝚎𝚜𝚜 𝚜𝚝𝚛𝚒𝚌𝚝 (𝚏𝚘𝚛 𝚎𝚟𝚎𝚛𝚢𝚍𝚊𝚢 𝚛𝚎𝚜𝚝𝚛𝚒𝚌𝚝𝚒𝚘𝚗𝚜):
-You can’t copy homework from your friend.
-You can’t interrupt your classmate while they are speaking.
b- 𝘴𝘵𝘳𝘰𝘯𝘨 𝘱𝘳𝘰𝘩𝘪𝘣𝘪𝘵𝘪𝘰𝘯 / 𝘳𝘶𝘭𝘦 (𝘴𝘦𝘳𝘪𝘰𝘶𝘴 𝘵𝘰𝘯𝘦):
-You 𝐦𝐮𝐬𝐭𝐧’𝐭 cheat in the exam.
-You 𝐦𝐮𝐬𝐭𝐧’𝐭 copy homework from your friend. (very strict)
5-𝘖𝘣𝘭𝘪𝘨𝘢𝘵𝘪𝘰𝘯 𝘤𝘰𝘮𝘦𝘴 𝘧𝘳𝘰𝘮 𝘰𝘶𝘵𝘴𝘪𝘥𝘦 𝘵𝘩𝘦 𝘴𝘱𝘦𝘢𝘬𝘦𝘳 (𝘦𝘹𝘦𝘮𝘱𝘭𝘦 𝘧𝘳𝘰𝘮 𝘢𝘥𝘮𝘪𝘯𝘪𝘴𝘵𝘳𝘢𝘵𝘪𝘰𝘯):
-I 𝗵𝗮𝘃𝗲 𝘁𝗼 submit the report before the end of the week.
6-𝘖𝘣𝘭𝘪𝘨𝘢𝘵𝘪𝘰𝘯 𝘤𝘰𝘮𝘦𝘴 𝘧𝘳𝘰𝘮 me/ the speaker (my own duty):
-I 𝙢𝙪𝙨𝙩 check the garden this evening.
7-N𝚘𝚝 𝚛𝚎𝚚𝚞𝚒𝚛𝚎𝚍” / “𝚒𝚝’𝚜 𝚘𝚙𝚝𝚒𝚘𝚗𝚊𝚕:
-You 𝙙𝙤𝙣’𝙩 𝙝𝙖𝙫𝙚 𝙩𝙤 come if you’re busy.
- 𝗗𝗼𝗻’𝘁 𝗜 𝗵𝗮𝘃𝗲 𝘁𝗼 bring a coffee to the meeting?
LearnEnglish team,
I would like to know the difference between can you, could you, will you, and would you?
I think these are not models of permission and application these are models of requests. How to use these models of requests in a grammatically acceptable way?
Thank you very much.
Hello ShetuYogme,
As you say, these are all phrases which can be used for requests. In terms of structure they are all followed by a bare infinitive. In terms of use as requests they are very similar in meaning with really only a difference in politeness/formality. You can read more and see more examples on these pages:
https://dictionary.cambridge.org/grammar/british-grammar/requests
https://learnenglish.britishcouncil.org/grammar/english-grammar-reference/requests-offers-invitations
Peter
The LearnEnglish Team
Hi again,
Can and will are informal; and; could and would are formal. If so, I would like to know the difference between
Thank you.
Hello again ShetuYogome,
The difference is small and in many situations you can choose between the pairs.
Can and could ask if something is possible. A person may be happy to do something but not have the time, for example.
Will and would ask if the other person agrees to something. A person may have the time but not be willing to do something, for example.
Peter
The LearnEnglish Team