A question tag forms a statement into a question. It is a short question form at the end of the sentence.
They are usually used in spoken English to confirm that something is true or false, or to encourage somebody to give a reply.
1. Question tags with auxiliary verbs.
It is easy to form the question tag, if an axiliary verb (form of be, can, do, must, may, shall, will) is used in the main sentence.
a) A positive statement is followed by a negative question tag:
He is a nice person, isn’t he.
We were at home, weren’t we?
We can eat at the hotel, can’t we?
I must go by car, mustn’t I?
You should do your homework, shouldn’t you?
A person/thing in the main clause needs to be changed to its personal pronoun in the question tag.
Anna was a good girl, wasn’t she?
The dog is dangerous, isn’t it?
The Smiths will go to Paris, won’t they?
b) A negative statement is followed by a positive question tag:
I won’t get a good mark, will I?
They weren’t at home yesterday, were they?
You aren’t vegetarian, are you?
2. Question tags with a full verb in the main sentence.
If the statement in the main clause is only a full verb, you have to use do(n’t)/does(n’) in the same tense of the main clause.
a) Positive statements
You eat hamburgers, don't you?
The children usually play in the garden, don’t they?
We watch a lot of TV, don’t we?
Stephen bought a new TV, didn’t he?
b) Negative statements
The auxiliary verb (do, is, am, are, can, etc.) is already used in the negative main clause, so we use it in the question tag too.
We didn’t lock the door, did we?
Penny doesn’t play with Lego, does she?