Have to, don't have to, must, mustn't
Learn how to talk about obligation, lack of obligation, and prohibition.
- check_circleI can talk about obligations and rules.
- check_circleI can say when something is not necessary.
- check_circleI can give strong advice and explain prohibitions.
Discover
Meet today's English in a real situation — no rules yet. Read it once and try to guess the pattern in the words in bold. Underlined words open a short definition.
Sarah: Hi, Mark! Welcome to the company. I’m going to explain some of the office rules.
Mark: Thank you, Sarah. What time do I have to start work?
Sarah: You have to arrive by 9:00 AM every day. But you don’t have to wear a suit. We are quite casual here.
Mark: That’s great! Can I eat at my desk?
Sarah: Yes, you can. But you mustn’t leave any food in the fridge overnight. The cleaners throw it away.
Mark: Got it. And what about parking?
Sarah: You must park in the visitor area today, but tomorrow you will get a permanent spot. Remember, you mustn’t block the emergency exit!
Mark: Understood. Thanks for the help!
Learn
Now the rules behind what you just saw — explained simply, with examples. Underlined words open a short definition — hover on desktop, tap on a phone.
We use have to, don’t have to, must, and mustn’t to talk about rules, obligations, and things that are necessary (or not).
1. Obligation: Have to / Must
Both have to and must mean that something is necessary. In spoken English, have to is much more common for general rules or daily obligations.
I have to wear a uniform at work. (It’s a rule)
You must stop at the red light. (Strong rule or written instruction)
Use have to for everyday rules (work, school) and must when you are giving strong advice or in formal written rules (like on signs).
2. Lack of Obligation: Don’t have to
Don’t have to means something is not necessary. You can do it if you want, but there is no rule or obligation.
You don’t have to work on Sundays. (It’s your choice)
She doesn’t have to cook tonight; we can go to a restaurant.
Don’t have to does NOT mean “don’t do it”. It means “it’s not necessary, but you can choose”.
3. Prohibition: Mustn’t
We use mustn’t (must not) to say that something is a bad idea or against the rules. It means “don’t do it”.
You mustn’t use your phone during the exam. (It’s against the rules)
We mustn’t be late for the meeting. (It’s very important not to be late)
Don’t have to and mustn’t are very different!
- You don’t have to go. (You can stay home, it’s okay)
- You mustn’t go. (Don’t go! It’s a bad idea or prohibited)
- Have to / Must: It is necessary. (I have to work).
- Don’t have to: It is not necessary. It’s your choice. (I don’t have to work).
- Mustn’t: It is prohibited. Don’t do it. (You mustn’t smoke here).
Practice
Try it yourself. You'll see right away whether you got it right, plus a short explanation of why.
Use It
Now make the language yours in a real task. Use the prompt below — the editor keeps a simple word count, and nothing is saved or graded.
Before you finish — be honest. Can you do these now?