Have to, must, should: Obligation, prohibition, necessity, advice
Learn how to express rules, give strong advice, and talk about what is necessary.
- check_circleI can talk about obligations and necessity using 'have to' and 'must'.
- check_circleI can explain what is prohibited using 'mustn't'.
- check_circleI can give advice using 'should'.
- check_circleI know the difference between 'don't have to' and 'mustn't'.
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.
Sam: Hey, Alex! I heard you got the job at the new tech company. Congratulations!
Alex: Thanks, Sam! I’m really excited, but also a bit nervous. I start on Monday, and there’s a lot of information to remember.
Sam: Don’t worry, you’ll be fine. What did they tell you during orientation?
Alex: Well, I have to arrive before 9:00 AM every day. They are very strict about punctuality.
Sam: That makes sense. Do you have to wear a uniform?
Alex: No, I don’t have to wear a uniform, but the dress code is business casual. Oh, and I mustn’t share any company secrets with people outside the office. We signed a confidentiality agreement.
Sam: Of course. You should definitely keep that in mind. Is there anything else?
Alex: Yes, my manager said I must attend the weekly team meeting on Wednesdays. It’s mandatory.
Sam: That sounds standard. My advice? You should get plenty of rest this weekend. You don’t have to learn everything on the first day, but you should try to make a good impression.
Alex: Thanks! I think I should also buy a nice notebook so I don’t forget anything.
Sam: Great idea! But remember, you mustn’t overwork yourself. It’s a marathon, not a sprint!
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, must, and should to talk about rules, obligations, and advice. Although they are similar, they have very different meanings when we use them in the negative!
Obligation and Necessity: Have to & Must
When something is necessary or required by a rule, we use have to or must. In many positive sentences, you can use either one, but have to is much more common in everyday spoken English.
- You have to wear a seatbelt in the car.
- I must finish this report by Friday.
Usually, we use have to when the rule comes from someone else (like a boss, the law, or a school). We use must when the obligation comes from ourselves (like a personal goal).
Prohibition vs. No Obligation
This is where many English learners make mistakes. The negative forms mustn’t and don’t have to have completely different meanings.
- Mustn’t (Must not) = It is prohibited. You are not allowed to do it. It’s a bad idea.
- Don’t have to = It is not necessary. You can do it if you want, but you are not obligated.
Common mistake! Spanish speakers often confuse no tener que with must not.
Incorrect: You mustn’t pay for the ticket, it’s free. Correct: You don’t have to pay for the ticket, it’s free.
- You mustn’t use your phone during the exam. (It is against the rules.)
- You don’t have to wear a suit to the party. (It is optional.)
Advice: Should
We use should and shouldn’t to give advice, make recommendations, or express what we think is a good idea. It is not as strong as must or have to.
- You should drink more water. It’s good for your health.
- We shouldn’t leave too late, or we’ll miss the train.
To make your advice sound a bit softer, you can add I think or I don’t think:
- I think you should apologize.
- I don’t think you should buy that car.
- Have to / Must: Obligation or necessity. (I have to work tomorrow.)
- Mustn’t: Prohibition. Do not do it! (You mustn’t smoke here.)
- Don’t have to: No obligation. It’s optional. (You don’t have to come if you’re tired.)
- Should / Shouldn’t: Advice or recommendation. (You should eat more vegetables.)
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?