Tag question are used mostly in spoken English, but can be used in written English too.
Tag questions are just basically used to confirm a statement.
The rules for tag questions are quite simple.
If the statement is positive, then the tag question is negative.
The tag question is made up of the subject and the auxiliary word. If there is no auxiliary word, than the tag question is usually made up of - do, does or did or another auxiliary verb
Examples of tag questions
I am a good student. Aren't I?
We have a great teacher. Haven't we? Or don't we?
This is my computer. Isn't it?
I don't like to go to school. Do I?
You don't live in New York City? Do you?
You are not coming to visit me today? Are you?
Is that your car? Isn't it?