In BrE there are two separate verbs need.
Need as a main verb has the question form do you need?, the negative you don't need and the past forms needed, did you need? and didn't need. It has two meanings:
1. to require something or to think that something is necessary:
Do you need any help ?
I needed to get some sleep.
2. to have to or to be obliged to do sth:
Will we need to show our passports?
Need as a modal verb has need for all forms of the present tense, need you? as the question form and need not (neednít) as the negative. The past is need have, needn't have. It is used to say that something is or is not necessary:
Need I pay the whole amount now?
In NAmE only the main verb is used. This leads to some important differences in the use and meaning of need in British and American English.
In NAmE it is more common for need to be used to speak about what is necessary, rather than about what you must do:
I donít need to go home yet - it's still early. (BrE and NAmE = it isn't necessary)
You donít need to go home yet - we never go to bed before midnight. (BrE = you don't have to.)
The difference is even more noticeable in the past tenses:
He didn 't need to go to hospital, but he went just to reassure himself. (NAmE)
He needn 't have gone to hospital, but he went just to reassure himself. (BrE = he did something that
He didn 't need to go to hospital after all - he only had a few bruises. (BrE= he didn't go.)
see: ALD, seventh edition 2005