Simple explanation
What do must and have to mean? Must and have to are used when an action is necessary or required. In many everyday situations, they have a similar meaning. For example, I must leave now and I have to leave now both mean that leaving is necessary. However, the reason for the obligation can make one form more natural than the other. When do we use must? We often use must when the speaker strongly feels that something is necessary or wants to give a strong instruction. It is also common in rules and notices. In I must call my mother tonight, the speaker personally sees the call as important and necessary. After must, use the base form of the verb without to. When do we use have to? Have to is very common in everyday spoken English. We often use it when an obligation comes from a rule, schedule, situation, job, school, or another person. For example, I have to wear a uniform at work suggests that the workplace or its rules make the uniform necessary. Have to and has to In the present simple, use have to with I, you, we, and they. Use has to with he, she, and it. For example, We have to leave at six, but Anna has to leave at six. Mustn't and don't have to have different meanings This is one of the most important points in this lesson. Mustn't means that an action is prohibited: you are not allowed to do it. Don't have to means that an action is not necessary: you can do it, but there is no obligation. You mustn't park here means parking is prohibited. You don't have to come early means coming early is optional. How do we ask questions with have to? To ask whether something is necessary, we commonly use do or does with have to. Use Do I have to...? and Do they have to...? With he, she, and it, use Does ... have to...? After does, use have, not has. How do we talk about past and future obligations? Must does not have separate forms for all tenses. For a past obligation, we normally use had to + base verb. For a future necessity, we can use will have to + base verb. For example, I had to work yesterday describes a past obligation, while I'll have to work tomorrow describes a future necessity.
Grammar formula
Obligation with must
Subject + must + base verbYou must wear a seat belt.
Obligation with have to
I/You/We/They + have to + base verbWe have to leave at six.
Obligation with has to
He/She/It + has to + base verbShe has to work today.
Prohibition
Subject + mustn't + base verbYou mustn't smoke here.
No necessity
Subject + don't/doesn't have to + base verbYou don't have to wait.
Question about necessity
Do/Does + subject + have to + base verb?Do we have to pay now?
Past obligation
Subject + had to + base verbI had to take a taxi.
Future necessity
Subject + will have to + base verbWe will have to leave early.
Core rules
- 1
Use must + base verb
Put the base form of the verb directly after must. Do not add to: must go, must study, must wait.
- 2
Use have to with I, you, we, and they
In positive present-tense sentences, use have to + base verb with I, you, we, and they.
- 3
Use has to with he, she, and it
In positive present-tense sentences, have changes to has with a third-person singular subject: He has to work.
- 4
Use mustn't for prohibition
Mustn't + base verb means that an action is not allowed. It does not mean that the action is simply unnecessary.
- 5
Use don't or doesn't have to for no necessity
Don't have to and doesn't have to mean there is no obligation to do something. The person may still choose to do it.
- 6
Use do or does in questions with have to
The usual pattern is Do/Does + subject + have to + base verb? After does, use have rather than has.
- 7
Use had to for past obligation
For an obligation or necessity in the past, normally use had to + base verb.
- 8
Use will have to for future necessity
For a necessity that will exist in the future, use will have to + base verb.
Useful examples
I must finish this report tonight.
I really need to finish this report tonight.
Must emphasizes that the speaker sees the action as important and necessary.
You must wear a seat belt in the car.
Wearing a seat belt in the car is required.
Must expresses a strong requirement or rule.
We have to get up early tomorrow.
It is necessary for us to get up early tomorrow.
A schedule or situation creates the necessity.
Mia has to take the bus to work.
It is necessary for Mia to take the bus to work.
Use has to with a third-person singular subject such as Mia or she.
You mustn't use your phone during the exam.
You are not allowed to use your phone during the exam.
Mustn't expresses prohibition.
You don't have to bring any food.
Bringing food is optional; it is not necessary.
Don't have to means there is no obligation.
Does Ben have to work on Saturdays?
Is Ben required to work on Saturdays?
After does, use have to, not has to.
Do I have to book a table?
Is it necessary for me to book a table?
Do I have to...? is a common way to ask about necessity.
My sister doesn't have to wear a uniform.
It is not necessary for my sister to wear a uniform.
Doesn't have to shows absence of obligation.
I had to stay at home yesterday.
It was necessary for me to stay at home yesterday.
Had to expresses an obligation or necessity in the past.
We'll have to buy some milk tomorrow.
It will be necessary for us to buy some milk tomorrow.
Will have to expresses future necessity.
Passengers must show their tickets before boarding.
Passengers are required to show their tickets before they board.
Must is common in rules and formal instructions.
I must remember to call David.
It is very important that I remember to call David.
The speaker personally feels that remembering the call is necessary.
We don't have to leave yet.
It is not necessary for us to leave yet.
There is no obligation to leave at this moment.
Common mistakes
- ❌ I must to go now. ✅ I must go now. Must is followed directly by the base form of the verb. Do not use to after must.
- ❌ She have to work today. ✅ She has to work today. With he, she, and it, use has to in positive present-tense sentences.
- ❌ Does he has to pay? ✅ Does he have to pay? After does, the verb returns to its base form, so use have rather than has.
- ❌ You don't have to smoke here. ✅ You mustn't smoke here. If smoking is prohibited, use mustn't. Don't have to only means that an action is not necessary.
- ❌ I musted work yesterday. ✅ I had to work yesterday. Must does not have a past form called musted. Use had to for past obligation.
- ❌ He doesn't has to come early. ✅ He doesn't have to come early. After doesn't, use the base form have.
Learning tips
- Remember the pattern must + base verb: must go, not must to go.
- Have to is very common when talking about everyday obligations.
- Use has to with he, she, it, and singular names in positive present-tense sentences.
- Remember the key contrast: mustn't means prohibited; don't have to means not necessary.
- Use Do I have to...? and Does she have to...? when asking whether something is necessary.
- Use had to when talking about an obligation in the past.
- Do not treat the difference between must and have to as an absolute rule. In some positive sentences, both are possible with only a small difference in emphasis.
Practise this topic
Interactive exercises for this topic are coming soon.
PlannedRelated grammar
Related dictionary words
Frequently asked questions
Can I use must and have to in the same situations?
Sometimes. In positive sentences, both can express a strong necessity. Must often emphasizes the speaker's view or a strong instruction, while have to is especially common for everyday obligations and requirements caused by circumstances. The difference is not absolute in every context.
What is the difference between mustn't and don't have to?
Mustn't means an action is prohibited, while don't have to means an action is not necessary. If you mustn't enter, entering is not allowed. If you don't have to enter, you can choose whether to enter.
Why do we say she has to but Does she have to?
In a positive present-tense sentence, have changes to has with she. When does is used to form a question, the following verb returns to its base form, so we say Does she have to...?
Can I say must to go?
No. Must is followed directly by the base form of the verb. Say must go, must work, or must study, not must to go.
How do I express obligation in the past?
Use had to + base verb for a past obligation. For example, I had to leave early means that leaving early was necessary in the past.
How can I ask if something is really necessary?
Use a question with have to. For example, Do I have to bring my passport? or Do we have to be there at eight? These forms are natural in everyday English.