"Must Not" or "Don't Have To"?

What's the difference between "must not" and "don't have to"?

Must Not

Must not = mustn't = this is not allowed / this is against the rules.

"You mustn't drive further."

Examples:

• "You mustn't smoke in here."
• "Kids must not drive."
• "You must not cross the road when there is a red light."

Don't Have To

Don't have to = this is not necessary / it's okay not to do it. 

"You don't have to buy from him."

Examples:

• "You can come with us to the trip, but you don't have to."
• "She doesn't have to work there. She can quit."
• "I don't have to agree with everything he says."

In summary, "must not" is a command not to do something, and "don't have to" leaves the choiceto you.

Quiz

Which of the following sentences is incorrect?

1. You mustn't smoke in here.
2. She doesn't have to come if she wants to stay home.
3. They mustn't donate if they prefer not to. 
4. We really don't have to talk about it.

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