Don't have to/ don't need to/ needn't (No obligation)

I don't have to go if is not necessary
You didn't need to get up early because yesterday you didn't have to go to school
Oh! I'm sorry! You needn't have got up early today! you don't have to go to school!
We needn't come together, I prefer take a taxi later
They don't have to work because their boss has married