obligation, prohibition and permission
Which is correct? Or both? You *need to / are allowed to* get a parking permit if you want to use the car park.
need to
Which is correct? Or both? Employees *have to / mustn't* attend at least three training days per year to receive a certificate.
have to
Which is correct? Or both? She *can't / doesn't have to* work with us if she doesn't want to. I just thought she might like to.
doesn't have to