Kilo Lingo
English grammar Part of Chapter 4

CEFR A2-B1

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Test yourself (23 questions)

Must, have to and should in English: rules and examples

By Michael McGettrickUpdated 12 October 2026

Must and have to say something is necessary. Should says it is a good idea. And one pair catches everyone: mustn't means do not do it, but don't have to means you can choose.

necessarya good ideado not do itnot necessary (you choose)What do the colours mean?
MeaningSentence
.
.
.
.
.

Quick check

Now use it: three quick questions on the chart above. The full practice is further down.

Pick the right one

0/3

Mustn't (do not do it) or don't have to (you can choose)?

  1. You pay. It's free.

  2. You touch that. It's very hot.

  3. You come with me. I can go alone.

How strong is it? From an idea to a must:

An ideaNecessary
  1. You could call her.one idea
  2. You should call her.a good idea
  3. You must call her.necessary

Must and have to: it is necessary

necessarythe part that changesWhat do the colours mean?

Both go before the base verb. After must there is no to; have to keeps its to.

WhoMustHave to
/ / / . .
/ / . .
With he, she and it: has to

Must never changes. Have to is an ordinary verb, so it changes, and it has every tense:

TimeExample
.
.
?
.

Must has no past. For yesterday, use had to: I had to go.

? In everyday speech both say it is necessary, and have to is more common. In British English there is often a small difference:

It comes fromExample
.
.

Should and shouldn't: a good idea

necessarya good ideaWhat do the colours mean?

Should gives advice: it is a good idea, but you can choose. Shouldn't says it is not a good idea.

SituationAdvice
. .
. .
. .
?

Should is softer than must:

  • . (it is a good idea)
  • . (it is very important)

Mustn't and don't have to

do not do itnot necessary (you choose)What do the colours mean?

These two look alike, but they say very different things.

WordsMeaningExample
: .
: .

Look at the same verb with both:

  • Tom. (do not tell him: it is a secret)
  • Tom. (you can tell him if you want)

Don't need to means the same as don't have to: . (you can go). In British English you will also hear needn't: You needn't wait.

Ought to and had better

Two more ways to give advice, for A2 and B1.

WordsMeaningExample
, formal .
: , .

Had better talks about now or soon, not the past, even with had. Its negative is had better not: You'd better not be late.

Common mistakes

WrongRightWhy
I must to go.I must go. .
She have to go.She has to go.: .
I must go yesterday.I had to go yesterday.: .
Do you must go?Do you have to go? .
You should to rest.You should rest. .

What to do next

  1. Say two things you have to do this week and one you don't have to do.
  2. Give a friend some advice with should.
  3. Back to modal verbs, or do the drills below.

Practise: test yourself

Sort into groups

0/6

Necessary, or advice? Sort each sentence.

Tap a word, then the group it belongs in.

Pick the right one

0/5

Mustn't (do not do it) or don't have to (you can choose)?

  1. You pay. It's free.

  2. You touch that. It's very hot.

  3. You come with me. I can go alone.

  4. You tell anyone. It's a secret.

  5. You wear a suit. It's a small party.

Spot the mistake

0/4

Each sentence has one mistake. Tap it.

Complete the story

0/4

Choose the words that fit each gap.

Ana's new job

It is a rule: Ana wear a uniform at work. Her boss is very strict, so she be late. On Saturday she can stay at home or go in: she work. Today she looks tired. Tom says: You go to bed early.

Gap 1 of 4

Matching

0/4

Match each sentence to what it means.

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Frequently asked questions

What is the difference between must and have to?
Often there is none: I must go and I have to go both say it is necessary. In British English, must often comes from the speaker (I must call my mum) and have to from a rule or another person (I have to wear a uniform). Have to is more common in speech, and in American English.
What is the difference between mustn't and don't have to?
Mustn't means do not do it: it is not allowed, or it is a very bad idea. You mustn't smoke here. Don't have to means it is not necessary, so you can choose. You don't have to come.
What is the past of must?
Must has no past form for necessity. Use had to: I had to work yesterday. Had to is the past of both must and have to.
Is it has to or have to?
Has to with he, she and it: she has to work. Have to with I, you, we and they: I have to work. In questions and negatives, use does and have: Does she have to work? She doesn't have to work.
What is the difference between should and must?
Should is advice: it is a good idea, but you can choose. Must is stronger: it is necessary. You should see a doctor (it is a good idea). You must see a doctor (it is very important).