A hardy Indianism made its appearance during the recently concluded men’s finals at Wimbledon. Vijay Amritraj, who was covering the match for Times Now, asked his fellow commentator: ‘He is very rattled, isn’t it?’ (Federer, at that point, appeared to be losing his cool. An official review of a shot had been called and it had gone against him.  I think I heard him say (after disputing the Hawkeye verdict), ‘shit’.
‘He is rattled. Isn’t it?’  This comes naturally to most, if not all, of us. English requires that the tag repeat the subject of the main clause with an appropriate pronoun. In this case the main clause subject itself is the pronoun he. The tag should repeat it. He is rattled, isn’t he?
‘Isn’t it’ is so much with us, it is an invariable tag in Indian English. She is working at Infosys, isn’t it? Raju is now engaged, isn’t it?  Verma’s parents are now in Delhi, isn’t it? The correct tags, of course, are: isn’t she?  isn’t he? aren’t they?
We may as well note some other features of tag questions. Not only is the subject repeated using a suitable pronoun; the auxiliary in the main clause is also repeated: Hema has joined the Art of Living Centre, hasn’t she? Rajesh would have agreed to the proposal, wouldn’t he? We should be leaving now, shouldn’t we?  Also, the tag is negative, if the main clause is affirmative, and affirmative, if the main clause is negative.  Vandana hasn’t taken up the job, has she?  Raju didn’t qualify, did he?  (In technical language this is referred to as polarity. The main clause in the last example shows one more feature of the tag question.  If the main clause has no auxiliary (i.e., no form of a BE or HAVE) the tag must have a form of Do.
The point about polarity needs to be modified.  There are tags which show no difference in polarity. Shekar has resigned, has he?  Goyal was taken into custody, was he?
Structures showing a difference in polarity generally seek confirmation of what is said in the main clause.  When there is no difference in polarity (as in the examples in the previous paragraph) the tag may express surprise, astonishment, anger, disbelief depending on the context.
The tag in IE is, already noted, invariant.  He (Federer) is rattled, isn’t it?  She is working at Infosys, isn’t it?
It is not just Indian English which has this invariant tag. In other languages too, e.g. some European languages) the tag is invariant.
This invariant tag may be explained as seeking confirmation of the truth of the ‘propositional content’ of the main clause. He is rattled, isn’t it? should be interpreted as:  ‘Isn’t it a fact that he is rattled.’
Such an analysis is not far-fetched but it does not conform to the intent of the English tag which seeks confirmation of what is said about the subject. The English tag is more limited in scope and direct; not so the invariant IE tag.
The difference between the two interpretations will become clear if we ask ‘Can it (in the IE version) possibly refer to the subject?’ It can’t. It can only refer to something which has no gender distinction – the proposition. This is not so with the Standard English tag where the pronoun can only refer to the subject. 
Where the subject is singular and inanimate or ‘dummy’ the distinction between the Indian tag and the Standard English tag disappears.  It is an anteater, isn’t it?  Amritaraj had this sentence: It (the situation at that point) is very tense, isn’t it?
Before closing it should be noted that not all types of sentences permit a tag question. There is no tag possible on an exclamation like ‘What a beautiful house!’ But a tag is possible in:  ‘Beautiful, isn’t it?’ (Because beautiful can be interpreted as:  ‘It is very beautiful’.  Questions don’t permit tags of the type we have been examining. What did you buy?  How far is it from here?  How did you manage to do it?  But tags of a different type are possible with some questions: Is that a complement, or what? Are we agreed on this, or what?  Is that Rashmi, or is she?  Then again it is only ‘yes no’ questions (i.e., question which can be answered with a ‘yes’ or ‘no’ that permit tags of this type.
As for imperatives they take a tag unique to imperatives, Get up, will you?  Stop that racket, will you? Shut the door, will you? These tags express some annoyance, irritation on the part of the speaker. (For some more advanced points on tags, see my book Structure, Style and Usage, OUP, 2005.  On the tag or what?  see English For You April 5, 2007.)
The writer can be contacted on ksyadurajan@yahoo.com
Maxims & Observations of Kay S. Wye.
The crocodiles in the Nile/Have usually a broad smile. / That’s because the bastards/ Often gobble up cowherds.