We often put small questions at the ends of sentences in speech.

• That's the postman, isn't it?    
• You take sugar in tea, don't you?
• Not a very good film, was it?
  

We use these 'question tags' to ask if something is true, or to ask somebody to agree with us.

Structure

We do not put question tags after questions.

• You're the new secretary, aren't you?
  (NOT Are you the new secretary, aren't you?)
  

We put negative tags after affirmative sentences, and non-negative tags after negative sentences.

• It's cold, isn't it?   
• It's not warm, is it?
  

If the main sentence has an auxiliary verb (or be), the question tag has the same auxiliary verb (or be).

• You haven't seen my keys, have you?
• The meeting's at ten, isn't it?

If the main sentence has no auxiliary verb, the question tag has do.

• Harry gave you a cheque, didn't'he?

Meaning and intonation
We show the meaning of a question tag by the intonation. If the tag is a real question — if we really want to know something, and are not sure of the answer — we use a rising intonation: the voice goes up.

• The meeting's at four о 'clock, isn't it?

If the tag is not a real question — if we are sure of the answer — we use a falling intonation: the voice goes down.

• It's a beautiful day,  isn't it?

Requests

We often ask for help or information by using the structure negative sentence + question tag

• You couldn't lend me a pound, could you?
• You haven't seen my watch anywhere, have you?

Note
a)    The question tag for /amis aren't I? I'm late, aren't I?
b)    After imperatives, we use won't you?(to invite people to do things) and will you? would you? can you?can't you?and cou/dyou?(totell people to do things).

• Do sit down, won't you?      
• Open a window, would you?
• Give me a hand, will you?   
• Shut up, can't you?

After a negative imperative, we use will you.

• Don't forget, will you?

After Let's ...  we use shall we?

• Let's have a party, shall we?

с) There can be a subject in question tags.

• There's something wrong, isn't there?
• There weren't any problems, were there?

d) We use it in question tags to refer to nothing, and they to refer to nobody.

• Nothing can happen, can it?    
• Nobody phoned, did they?