USAGE

Question tags are little questions that people often use at the end of a sentence when talking. They can be used to make sure something is true/correct or to ask for agreement.

- You want coffee, don't you?
- You have seen the film, haven´t you?
- She's Irish, isn't she?

They are very common and useful because it is an easy and quick way to keep people's attention and force them to say something, so we can keep the conversation going.

- It's very cold today, isn't it?
- Oh yes, I think so.

FORM

You can only make a question tag using a special verb (modals and auxiliaries), so if the main verb in the sentence is a normal verb, then we use DO to make the question tag. But if the main verb is a special verb, we use that special verb for the question tag. The question tag will be in the same tense as the verb in the main clause.

- You like coffee, don't you?  (like: normal verb)
- You can help me, can't you?  (can: special verb)
- He is Mr Smith, isn't he ?
- They're making tea, aren't they?
- Your father will be there by ten, won't he?
- You've been to London, haven't you?
- Susan bought a new house,  didn't she?

We usually use an affirmative question tag after a negative sentence
- It isn't  very cold, is it?
- Mark can't speak French, can he?
- Your cousins didn´t come to visit us, did they?

And a negative question tag after an affirmative sentence
- It is very cold, isn't it?
- She likes this film, doesn't she?
- Your friend is going to come, isn't he?

And you must always use contractions in your question tags because a question tag without contraction sounds terribly pedantic!
- You are Tim, are you not?  (*#Ⱥʬʘᴟ₩҉ !!)

MEANING

The meaning of a question tag depends on the intonation: A falling intonation is just looking for agreement, a rising intonation is a question, looking for confirmation or correction.

- Kelly will come later, won't she? ↗
- No, I think she won't come because she was feeling ill today.

- Kelly will come later, won’t she? ↘
- Sure, don't worry. She'll be here in a few minutes.

THE THREE BASIC RULES TO REMEMBER

❶ Question tags always use a special verb
❷ The subject is always a pronoun, and it is inverted (because it is a question, of course)
❸ Affirmative sentences add a negative question tag and negative sentences add an affirmative question tag

SPECIAL CASES

I AM

The negative question tag "am I not" has no contraction. Because a question tag with no contraction sounds very pedantic, we prefer a very ungrammatical constraction but which is correct for question tags: "aren't I?"

- I'm late, aren't I?
- I'm talking to the walls, aren't I?
 
SUGGESTIONS

After a sentence with Let's... we use "shall we?"
 
- Let's go out for a walk, shall we?
- Let's study tomorrow morning, shall we?

IMPERATIVES & INVITATIONS

After an imperative we use "will you?" (always affirmative). We can consider "will you?" as an equivalent to "please" (more or less)
 
- Open the door, will you?
- Don't smoke in this room, will you?
- Come to my party, will you?
- Have a coffee, will you?
- Don't look at me like that, will you?

If there are two verbs in the sentence, the question tag may refer to one or the other, you must use your common sense here:

- I think you're John, aren't you? (= are you John?)
- I think you're John, don't I (= do I think...?)  [this would be correct but very rare]