3

Regarding the question in the title, I think we should use it:

That's a good one, isn't it?

'Isn't that' is respectively rare in this position, but I'm not sure if it's incorrect.

My question is: should we always use it in the question tag instead of this or that?

4

With This/That we use it in the question tag. So the usage of isn't it in the question tag is right.

When These/Those is used in the main sentence, the sentence requires They in the question tag. For Ex. These are good, aren't they?

Source

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  • I was hoping for a reference to call it downright wrong to use "isn't that?" as a question tag, but I guess this and my thorough search in the web should be enough now. Thnx. +1. – Færd Dec 4 '15 at 12:46
  • Usage of "isn't that" in question tag is wrong. I have never seen it being used this way. @MJF – Ashish Singh Dec 4 '15 at 12:50

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