Learn English – Common tag question for “must”


In this question, the OP wrote this:

She must leave early, mustn't she?

But I read this sentence here:

You must go, needn't you?

I read about must have here, but it doesn't say explain a lot about must as present modal. I only found this sentence:

He must use the lift, mustn't he?

Which one is correct here?
Also, these are confusing me too:

You must be tired, ____?

That guy must be rich, ____?

You must visit me every day, ____?

You don't seem to be a happy couple. You guys must fight a lot, _____?

According to what I can understand, the word must has several forms of tag questions.

I have googled and read some references, but the explanations seem to be overlapping.

Best Answer

Safari, I meant I didn’t really see what your question was and examples of what you consider wrong answers might have helped.

‘You must go, needn't you?’ has the right structure but the words are mismatched.

‘You must go, mustn't you?’ corrects the mismatch.

‘You need to go, needn't you?’ would be wrong because of the different verb form. ‘You need to go, don't you?’ would correct that.

There are obvious endings for your examples but I’m not sure I’ve understood the question.

‘You must be tired, mustn’t you?’

‘That guy must be rich, mustn’t he?’

‘You must visit me every day, mustn’t you?’

‘You guys must fight a lot, mustn’t you?’ is correct, but we might be just as likely to hear ‘You guys must fight a lot, don’t you?’. That's because the ‘must’ seems unnecessary; ‘You guys fight a lot’ would be simpler, and lead us to expect ‘don’t you?’