The modal verbs need and dare can take the auxiliary verb to do to form their negative and interrogative forms or they can do without it. In the former case they are usually followed by the to-infinitive and in the latter case by the bare infinitive. Need is mostly used to express necessity especially in negative sentences where it express the absence of necessity.

- Shall I go to the post office?
- No you needn't.

- Мне сходить на почту?
- Нет, не нужно.

Note: One should distinguish between the modal verb need (followed by the Infinitive) and the ordinary verb need (followed by a noun or a pronoun).

- Do you need this book now?
- Тебе нужна эта книга?

It always takes the auxiliary verb to do.

- May I take this book?
- I don't need it you may take it.

- Можно я возьму эту книгу?
- Она мне не нужна, бери.

- How dare you speak to me like this?
- Как ты смеешь так говорить со мной.

- He didn't dare to approach her.
- Он не осмеливался подойти к ней.