The basic tag questions are general English, shared by British and American:
informational: ‘You don’t wear glasses, do you?’ (I’m not sure, but think you don’t. Am I right?)
inclusive: ‘It’s a nice day, isn’t it?’(It obviously is – I’m not really asking, but just making polite remarks so you can join in the conversation).
emphasizing: ‘I made a bad mistake, didn’t I?’ (This is a soliloquy. I’m not talking to anybody but myself and don’t expect an answer to the rhetorical question. It’s the verbal equivalent of underlining.)
The last of the above types is more characteristic of British than of American use, but the next two are distinctively British and are relatively recent contributions of British English to the rhetorical inventory of impoliteness:
peremptory: ‘Is the tea ready?’ ‘The water has to boil, doesn’t it?’ (Everybody knows you can’t make tea without boiling hot water, and you can see that the water has not come to a boil yet, so stop bothering me with idiotic questions.)
antagonistic: ‘I telephoned you this morning, but you didn’t answer.’ ‘I was in the bath, wasn’t I?’ (The reason I didn’t answer was that I was in the bath, and it was a great annoyance having you phone at that time; if you had any sense and consideration, you would not have called then. [Never mind that the caller could not possibly know all that – I was annoyed at the time and I’m even more annoyed now at what I perceive to be a complaint when I am the one who was put upon.])
SOURCE: http://www.pbs.org/speak/ahead/change/ruining/
