不用 (don't need to)

My treat

• You take a friend to lunch, and she reaches for her wallet.
• don't need to不用bú yòng给钱gěi qián，I / me我wǒto give a dinner party请客qǐng kè。 — "You don't need to pay — it's on me."

don't need to不用bú yòng + Verb = don't need to

• don't need to不用bú yòng + Verb = "there's no need to": don't need to不用bú yòngworry担心dān xīn, don't need to不用bú yòngpolite客气kè qì, don't need to不用bú yònggo去qù.
• It is the usual negative of want / will / need要yào / (degree marker)得de (must) when something is unnecessary.

you你nǐdon't need to不用bú yòngworry担心dān xīn。

Polite replies

• A: thanks谢谢xiè xie！ B: You're welcome不用谢bù yòng xiè。 — "No need to thank me."
• A: want / will / need要yàoI / me我wǒto help帮忙bāng máng(yes/no ?)吗ma？ B: don't need to不用bú yòng(completed / change)了le，thanks谢谢xiè xie。 — "No need, thanks."

no need不用bú yòng了le，thanks谢谢xiè xie。

Not "don't use", not "mustn't"

don't need to不用bú yòng versus don't别bié

• don't别bié + Verb = "don't (do it)", an order: don't别biégo去qù！
• don't need to不用bú yòng + Verb = "you needn't", kinder and lighter: don't need to不用bú yònggo去qù(completed / change)了le — "No need to go any more."

don't别biégo去qù！

Recap

Read the full reference: HSK 4 grammar — Auxiliary verbs.