Must and Have To
Must and have to both say that something is necessary. Both go in front of a base verb, and in many sentences either one is fine.
When there is a difference, must is usually the speaker's own feeling, and it is also common in written rules. Have to is usually about a law, a rule or a situation.
MUSTI feel it is necessary
I must call my mum tonight.
Nobody is making me. I feel it is important.
HAVE TOa rule at work
I have to wear a uniform at work.
My job makes it necessary.
Must and have to both mean it is necessary, but mustn't means it is not allowed, and don't have to means there is no need.
TRY IT
- Question 1
"You touch that — it's very hot."
- Question 2
"It's Sunday. I go to work."
The forms
MUST
SmustV
You must wear a helmet.
The same for every subject, with no to after it.
MUSTN'T
Smustn'tV
Children mustn't play near the road.
Mustn't = must not: it is not allowed.
HAVE TO
Shave / has toV
She has to work on Saturdays.
Has to for he, she and it; have to for everyone else.
DON'T HAVE TO
Sdon't / doesn'thave toV
He doesn't have to cook tonight.
No need. After doesn't it is still have to, not has to.
QUESTION
Do / DoesShave toV?
Does he have to wear a tie?
Asked like an ordinary verb. Short answers: Yes, he does. / No, he doesn't.
PAST
Shad toV
We had to wait for an hour.
Must has no past form, so the past of both is had to.
HAVE TO CHANGES, MUST DOES NOT
- she + have toshe has to
- past + have tohad to
- she + mustshe must
- past + musthad to
Have to changes for person and tense like an ordinary verb. Must never changes: no musts, no must to, no musted.
TRY IT
- Question 1
"My brother must his homework first."
- Question 2
"Our teacher get up at six."
- Question 3
"We missed the last train, so we take a taxi."
When to use each one
Laws and rules
Drivers have to stop at a red light.
Somebody else made the rule, and everyone follows it.
Signal words: laws · school rules · rules at work
Your own feeling
I must clean my room this weekend.
Nobody is making you; you are reminding yourself.
Signal words: I must … · a reminder to yourself
Not allowed
You mustn't use your phone in the exam.
Something you are not allowed to do.
Signal words: mustn't · not allowed
Not necessary
The museum is free, so you don't have to pay.
You can do it or not. It is your choice.
Signal words: don't have to · no need
Mustn't vs. Don't Have To
In positive sentences, must and have to mean almost the same. In negative sentences they are very different: mustn't means it is not allowed, and don't have to means it is not necessary.
| MUSTN'T — NOT ALLOWED | DON'T HAVE TO — NOT NECESSARY | |
|---|---|---|
| In a test | You mustn't talk during the test. | You don't have to answer every question. |
| At work | You mustn't be late for meetings. | You don't have to wear a suit on Fridays. |
| Medicine | You mustn't take more than two tablets a day. | You don't have to take them with food. |
TRY IT
- Question 1
"This is a secret. You tell anyone."
- Question 2
"Ngọc has a car, so she take the bus."
Common mistakes
Incorrect:Children under six mustn't pay for the bus.
Correct:Children under six don't have to pay for the bus.
The writer means paying is not necessary for young children, but mustn't says paying is not allowed. No need is don't have to.
Incorrect:He must to leave now.
Correct:He must leave now.
Must goes straight in front of the base verb. The to belongs only to have to.
Incorrect:She musts finish the report.
Correct:She must finish the report.
Must never takes -s, not even with he, she or it.
Incorrect:Last week we must stay at home.
Correct:Last week we had to stay at home.
Must has no past form, so a sentence about the past uses had to.
Incorrect:My father have to work at night.
Correct:My father has to work at night.
My father is he, so have to becomes has to.
Incorrect:Do I must bring my passport?
Correct:Do I have to bring my passport?
Must does not go with do. To ask whether something is necessary, use Do I have to…?
Quick check · 6 questions
Choose the correct form:
Visitors must take off their shoes at the door.
- A. take off — Correct
- B. to take off
- C. taking off
Answer: A. take off
The word to never comes after must, and the verb after it has no -ing.
Choose the correct form:
Linh has to take the bus to school.
- A. has to — Correct
- B. have to
- C. must to
Answer: A. has to
Have to changes like have: he, she and it take has to. Linh is she, so use has to.
Choose the correct form:
The lift was broken, so we had to use the stairs.
- A. had to — Correct
- B. must
- C. musted
Answer: A. had to
The sentence is about something that already happened, and must has no past form. Musted is not a word.
Choose the correct words:
You mustn't swim here — the water is too deep.
- A. mustn't — Correct
- B. don't have to
Answer: A. mustn't
The water is too deep, so swimming here is not allowed. Don't have to only means swimming is not necessary.
Choose the correct words:
Tomorrow is a holiday, so the children don't have to go to school.
- A. don't have to — Correct
- B. mustn't
- C. doesn't have to
Answer: A. don't have to
On a holiday, going to school is not necessary, but nobody stops the children. The children means they, so use don't, not doesn't.
Choose the word that starts the question:
Do you have to work this weekend?
- A. Do — Correct
- B. Must
- C. Are
Answer: A. Do
Have to makes questions like an ordinary verb: Do you have to…? Are does not go with have to.
See whether it really stuck.
Start the quiz · 14 questions
