A tag question is a special construction in English. We usually use them for checking information that we think we know is true or for asking for confirmation that we have heard something correctly. They are very common in English.
If the main clause is positive, the question tag is negative.
You are tired (positive), aren’t you (negative)?
If the main clause is negative, the question tag is positive.
You aren’t tired (negative), are you (positive)?
If the main clause has an auxiliary verb, you use the same verb in the question tag. When there is no auxiliary verb (in the present simple and past simple) use do / does / did.
We have seen that, haven’t we ?
You are coming, aren’t you?
There is one notable exception to the rules.
After I am you use aren’t I in the question tag.
I am right, aren’t I?
Simple present ‘to be’
Phill is a teacher, isn’t he?
Simple present other verbs
She speaks Bulgarian, doesn’t she?
Elisa is studying in Oxford, isn’t she?
Simple past ‘to be’
Last winter was really cold, wasn’t it?
Simple past other verbs
Olivier talked to Benoit yesterday, didn’t he?
You were living in China, weren’t you?
We’ve visited Europe, haven’t we?
Present perfect continuous
We’ve been learning about Ancient Greece recently, haven’t we?
Emilia had left her books at the library, hadn’t she?
Past perfect continuous
Maria and Daria had been running, hadn’t they?
Simple future (with ‘will’)
Your grandparents will come next month, won’t they?