Question tag

[lille82]

Could anybody please explain why it is not correct to use "haven`t you" in this question tag?
"You have a BMW, dont`t you?"
Is it similar to the sentence below where need is used as a main verb not an auxiliary verb?
"They need to go now, don`t they?" is it correct anyway?

[bhaisahab]

Could anybody please explain why it is not correct to use "haven`t you" in this question tag?
"You have a BMW, dont`t you?"
Is it similar to the sentence below where need is used as a main verb not an auxiliary verb?
"They need to go now, don`t they?" is it correct anyway?

It's not incorrect. Who told you it was?

[lille82]

I have the first sentence "You have a BMW, don't you?" in my test book. I was just trying to figure out why can't I use "haven't you".
Also I am not sure how question tags are formed in sentences with "need" as a main verb and "need" as an auxiliary.

[5jj]

I have the first sentence "You have a BMW, don't you?" in my test book. I was just trying to figure out why can't I use "haven't you".

In American English, "don't you?" is, I believe, more common. In British English, "haven't you?" is more common, though I am hearing "don't you?" more these days. With "You've/You have got ...", only "haven't you?" is acceptable.

Also I am not sure how question tags are formed in sentences with "need" as a main verb and "need" as an auxiliary.

He needn't work, need he?
He doesn't need to work, does he?

[SoothingDave]

That's correct, "don't you?" would be common in AmE.

I don't think I've ever said "need he?"

[lille82]

Thank you for your help.

What about the question tag in this sentence: One needs to be punctual.
If it is correct to say "He doesn`t need to work, does he?" then "They need to work, don't they?" is fine as well, isn't it?

[5jj]

What about the question tag in this sentence: One needs to be punctual.

...doesn't one?

If it is correct to say "He doesn`t need to work, does he?" then "They need to work, don't they?" is fine as well, isn't it?

Yes. 'Need' is a lexical verb in those sentences, not a modal.