You Must/Mustnt Forget To Do Your Homework

Home Grammar intermediate Modals: must, have to, should, should have

Modals: must, have to, should, should have

Should

We use "should" to give, or ask for, advice or an opinion in the present:
  • "I have a terrible stomachache." "You should go to the doctor's."
  • "I haven’t heard from my father." "You should call him."
  • "She's not happy with the salary offered." "She shouldn't accept the job."

Form

We use

Example

I
You
He, She, It
We
They
should do more exercise.
get a new car.
shouldn't
(should not)
smoke.
spend so much money.

Should I
you
he / she / it
we
they
get more qualifications?
wear something different?

Should have

We use "should have" to give, or ask for, an opinion in the present about something which happened in the past:
  • "I had a terrible stomachache." "You should have gone to the doctor’s."
  • "I didn’t hear from my father last week." "You should have called him."
  • "She isn't happy with the salary she’s getting." "She shouldn't have accepted the job."

Form

We use

Example

I
You
He / She / It
We
They
should have taken a taxi.
shouldn't have written that comment.

Should I
you
he / she / it
we
they
have worked overtime?

Practice

Give or ask for advice using the verb in brackets:

Have to

"Have to" is used to show that a person is obliged to do something, usually by an outside force, have to can also be used to give your opinion:
  • You have to show your passport at passport control.
    (It’s the law.)
  • Jenny has to do homework every evening.
    (Her parents told her to do her homework.)
  • Tom had to work late last night.
    (He hadn't finished his work)
  • You have to tell him!
    (That's my (strong) opinion)
  • You don’t have to eat that if you don’t like it.
    (I am not obliging you to eat it)

The negative form, "don't" / "doesn't" / "didn't have to", means that you are not obliged to do something.

Form


or


Example

I
You
We
They
have to leave the house early to catch the bus.
care for the children.
He / She / It has to
I
You
We
They
don't have to leave the house early to catch the bus.
care for the children.
He / She / It doesn't have to

Do I
you
we
they
have to work on Saturday?
Does he / she / it attend the conference?

I
You
He / She / It
We
They
had to leave the house early to catch the bus.
care for the children.
I
You
He / She / It
We
They
didn't have to leave the house early to catch the bus.
care for the children.

Did I
you
he / she / it
we
they
have to work on Saturday?
attend the conference?

Practice

Give or ask for advice using the verb in brackets:

Must

"Must" is also used to talk about obligation and is used in written rules and instructions:
  • You must submit your proposal by noon on 12th July.
  • You must not use a calculator during the exam.
"Must" is also used to give a strong recommendation:
  • You must tell him before it's too late.
  • You mustn't be late for work on your first day.

The negative form, "mustn't" ("must not"), means that you are obliged or recommended not to do something.

Form



Example

I
You
He / She / It
We
They
must
mustn't
report the theft to the police immediately.
forget to transfer the money.

Must I
you
he / she / it
we
they
go?

While questions with "must" are grammatically correct, it is more usual nowadays to use "have to" for questions.

There is no past form of must for obligation:
  • We had to show our passports at the border.
  • We weren’t allowed to use calculators in the exam.
    Or, we couldn’t use calculators in the exam.

Practice

Give or ask for advice using the verb in brackets:

Further practice

Choose the correct answer to complete the sentence: a, b, c or d.



Check my answers

English Grammar: Modals of Obligation

When we talk about obligation in English, we can use "must", "have to", "need to" and "can't".

To say something is necessary

Must

We use "must" to talk about obligations. Often, when we use "must", the authority for the obligation comes from the person who is speaking.

Examples:

"You must do your homework every night." (Because I say you must!)

"I must stop smoking!" (Because I think it's a good idea to stop.)

Remember that "must" is a modal auxiliary verb. This means that it doesn't change its ending (I must, he must, etc) and that it's followed by the infinitive without 'to'. ("You must phone me" not "You must to phone me".)

For more information on modal auxiliary verbs, see our page on ability.

Have to

We can also use "have to" to talk about rules and regulations. The authority for the obligation doesn't come from the person who is speaking. Perhaps the rule is a general law or obligation.

"In England you have to pay tax."
"We have to check everyone's ID."

"Have to" is a normal verb. Use "do" or "does" to make a question, and "don't" or "doesn't" to make a negative.

"Do you have to vote in an election?"
"He doesn't have to wear a uniform to school."

Have got to

"Have got to" is common in British English and is stronger than "have to".

"I have got to fill in this form. The deadline is tomorrow."
"She has got to study hard to pass the exam."

To make the question and negative form, use "have", "has", "haven't" and "hasn't":

"Have you got to leave early tomorrow?"

Need to

We use "need to" to talk about what is necessary.

Examples:

"You need to go to the hairdresser's. Your hair is very long."
"She needs to go to the doctor. She gets headaches every day."

"Need to" is like "have to": use do / does to make questions:

"Do you need to pass an exam to get into university?"
"Does she need to get a job?"

To say something isn't an obligation

To say there is no obligation, use "don't / doesn't have to" or "don't / doesn't need to".

Examples:

"You don't have to bring food on the trip."
"She doesn't have to work in the evening."

"I don't need to pay now. I can pay later."
"They don't need to speak English in their job."

Typical grammar mistake! Be careful when you use "don't have to". It does not mean the same as "mustn't" - see below.

To say something is forbidden

To say that there is an obligation not to do something, use "mustn't".

"You mustn't play here - it's dangerous!"
"He mustn't eat peanuts. He's allergic to nuts."

We can also use "can't":

"You can't go out tonight. You've got homework."

Other expressions

be allowed to

"We're allowed to take an hour for lunch."
"We aren't allowed to leave early."
"Are you allowed to use the internet at work?

should

Should is a weak obligation, and we use it to give advice.

"You should study hard so you can pass the exam."
"He should see a doctor."

The negative form is "shouldn't":

"You shouldn't smoke. It's bad for your health."

Now try the grammar test below!

Need more practice? Check out our quiz on using can and have to.

Now go to the next page for vocabulary to talk about your job: English Vocabulary: Jobs and Work


Back to the main English Course page








1. Can you tell Deborah that she must __ me tomorrow?
2. __ pay in advance?
3. He __ learn to read and write his name before he goes to school.
4. We have __ early tomorrow.
5. __ wear a uniform?
6. I __ get up early tomorrow.
7. She __ work at the weekend.
8. You __ play football here. It's dangerous.
9. We __ attend all the lessons. We can choose.
10. I __ forget to call him tonight.
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