Question tags

Structure: Auxiliary and modal verbs + Personal Pronouns?
                                                   

 Main setence: Affirmative,            Question tag: Negative and vice versa
                        Interrogative              

Informal writing or ends of sentences in speech 
Not a very good film, was it?
No es una buena película, ¿verdad?

That's the postman, isn't it?
Es el cartero, ¿sí? 

Negative
Informal
You do take sugar in tea, don't you?
Te pones azúcar en el té, ¿sí?
 
Formal
They promised to repay us within six months, did they not? 
Prometieron reembolsarnos dentro de seis meses, ¿sí?  

Uses:
1. To check whether something is true 
    
2. To ask for agreement
    
3. Requests: Negative statement + question tag
    You couldn´t lend me a pound, could you?
   ¿Podrías prestarme una libra, no?



Bibliography
Swan, Michael. Practical English Usage, 1998. Oxford. Pag.478-479