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modals

grammar for IELTS : have to and don’t have to

Please please please read the following and try to use have to and don’t have to correctly. Have to and don’t have to are not opposites. They are related but they are not opposites. Many English language students make the mistake of thinking that, because mustn’t is the opposite of must, don’t have to is the opposite of have to. This is not the case!!

Look at these sentences and read the notes after them:

You must speak English in the IELTS exam.

In this sentence, must is an obligation to do something. You have no choice. It is a rule or law and cannot be broken.

You mustn’t speak your own language in the IELTS exam.

Mustn’t is an obligation not to do something. You have no choice. It is a rule or law and cannot be broken.

Have to is very different. make sure that you read the following and can understand the difference.

You have to speak English in the IELTS exam.

Have to is an obligation and its meaning is very similar to must. It is an obligation to do something. Must implies that you have the authority to make a rule or place an obligation on someone (including yourself.) Have to suggests that the rule was made by somebody else. In practice, this difference is very subjective. An IELTS examiner might say either of the following sentences:

You must speak English in the IELTS exam.

Here the examiner is the rule maker. The examiner is the authority.

You have to speak English in the IELTS exam.

Here the examiner is referring to the rule set by the examining body.

In effect, the two sentences mean the same thing and would have the same desired effect.

When we use don’t have to in a sentence, the meaning of have to changes.

You don’t have to wear a suit in your IELTS exam.

Don’t have to tell us that it is not necessary for you to do something but you can, of course, do it if you wish. It is permission not to do something. If you wear a suit, there will be no negative consequences. If you don’t wear a suit, there will also be no negative consequences. It is the opposite of can, a modal which gives permission to do something. It is similar in meaning to don’t need to/needn’t.

Here’s a summary of what we’ve just looked at:

obligation permission
to do things must
have to
can
allowed to
not to do things mustn’t
not allowed to
don’t have to
don’t need to
needn’t

Notice that not allowed to and allowed to are not really opposites of each other.

You are allowed to smoke in here.

This means that if you wish to smoke you can. You aren’t obliged to smoke.

You are not allowed to smoke in here

This means that smoking is prohibited and if you do so, there will probably be consequences.

speed limit 50

Look at this sign. I am sure you have seen something similar on the roads in your country. Can you make some sentences about it using the words in the table above? Try to use words from all of the boxes in the table if you can.

Here are some example sentences:

You must drive slower than 50 mph.
You mustn’t drive faster than 50 mph.
You can drive at speeds of up to 50 mph.
You don’t have to worry about the police if you are driving under 50 mph.

Can you say what these signs mean? Try to use words from more than one box in the table.