• We use have to to talk about strong obligation that comes from somewhere else, for example from you boss, you parents, a rule at school or work.

  Examples:
  
  I have to be home by ten. (My parents told me so.)
  I must be home by ten. I have a very difficult day tomorrow. (It is my own decision.)
  
  I have to get up early, because I start work at 8. (It is a rule.)
  I should get up early. (Now I stay in bed until lunchtime.)

• Don't have to means that there isn't any obligation at all,
  there is no need to do it.

  Don't have to is different from shouldn't and mustn't.

  Examples:
  
  I don't have to get up early at weekend.
  (I can stay in bed as long as I want.)
  
  You mustn't tell lies. (It is very bad to tell lies.)
  
  You don't have to go with me.
  (You can go with me if you want to.)
  
  You shouldn't smoke. (It is bad for your health.)
  

• In spoken British English you can also use have got to and haven't got to.

  Examples:
  
  Pamela is a waitress. She's got to work at weekends.
  Have I got to do it right now?
  I haven't got to take my sister to school, my parents do it.
  

Tip! We do not use have to when we talk about what is a good idea to do, but we don't do it yet. Instead, we use should.