Have to, must, should: Obligation, prohibition, necessity, advice

Grammar / B1 Grammar lessons and exercises \ Have to, must, should: Obligation, prohibition, necessity, advice

✏️ Exercises

Must / Mustn’t, Have to / Don’t Have to

Grammar chart comparing 'must', 'mustn't', 'have to', and 'don't have to'. Designed for A2/B1 English learners.

🟦Form: Have to vs Must

✅ Have to

Not a modal — needs “do/does/did” for negatives/questions:

  • ❌ Have you to get up early? → ✅ Do you have to get up early?
  • ✅ We don’t have to stay until the end.
  • ✅ I had to cancel the meeting.
  • ✅ She’s had to work weekends.

✅ Must

Modal verb — no auxiliary needed. Only present form:

  • ✅ I must go to the doctor.
  • ✅ You mustn’t call me before 8.
  • ❌ I musted go → ✅ I had to go.
  • ✅ Must I pay now? (formal/rare)

🟩Informal: Have got to

In spoken English, replace have to with ’ve got to:

  • I ’ve got to go to the supermarket.
  • She hasn’t got to be there until 10.
  • Have you got to leave so soon?

🟪Use: Must vs Have to — Obligation Source

Grammar chart comparing 'must', 'mustn't', 'have to', and 'don't have to'. Designed for A2/B1 English learners.

✅ Have to

External rules, laws, schedules, or other people’s demands:

  • You have to drive on the left in England.
  • I’ll have to get up early — exam at 8.
  • We had to wear uniforms at school.

✅ Must

Speaker’s personal opinion, belief, or strong advice:

  • You must eat less candy. (I’m telling you!)
  • We must get up early to finish painting.
  • You must see that film — it’s amazing!

🟨Mustn’t vs Don’t Have To — Opposite Meanings!

✅ You mustn’t wait here. → It’s forbidden.
✅ You don’t have to wait here. → It’s optional. You can leave if you want.

❌ Don’t confuse them — they mean very different things!

Mustn’t = prohibition (you are NOT allowed)
Don’t have to = no obligation (you can choose)

🟥Alternatives to Mustn’t

You can use can’t or be not allowed to instead of mustn’t:

  • You mustn’t smoke here. = You can’t smoke here. = You are not allowed to smoke here.
  • Children mustn’t eat gum. = Children can’t / aren’t allowed to eat gum.

🟦Should / Shouldn’t & Ought to

For advice or opinion — less strong than must:

✅ Should / Shouldn’t

  • You should go to a therapist.
  • Schools shouldn’t sell soft drinks.
  • You should be patient with me. (advice)

✅ Ought to / Ought not to

More formal, less common:

  • You ought to apologize.
  • You ought not to be so strict.

💡 Compare strength:
You must be quiet. (strong obligation)
You should be quiet. (good advice)
You ought to be quiet. (formal suggestion)

📌 Remember:
Have to = external obligation, all tenses, needs “do/does/did”
Must = speaker’s opinion, only present, no auxiliary
Mustn’t = prohibition (NOT allowed)
Don’t have to = no obligation (optional)
Should = advice (weaker than must)
Ought to = formal should
🔄 Can’t / not allowed to = mustn’t