Tag questions are sentences with short questions, or tags, at the end of them. For example:
“Keith is good at darts, isn't he?”
(A comma separates the first part of sentence from the tag.)
Tag questions can be formed using the first modal or helping verb (a form of “have” or “be”) in a verb phrase:
“Christine has been sick, hasn't she?”
“The storm won't last much longer, will it?”
“You can't fix this, can you?”
“Glen is being greedy, isn't he?”
Or the correct form of the verb “to do” (with sentences that have only one word in the verb phrase):
“They canceled the trip, didn't they?”
“She runs in marathons, doesn't she?”
“Warren lied to his mother, didn't he?”
“Birds fly south in the winter, don't they?”
Remember, tags are always positive if the sentence is negative, and negative if the sentence is positive.
“Carl isn't finished yet, is he?”
“The lights didn't get turned off, did they?”
“The police are looking for him, aren't they?”
“Sarah signed the contract, didn't she?”
Notice that contractions (can't, doesn't, won't) are usually used in the negative sentences and negative tags of tag questions.
“The test won't be difficult, will it?”
“David is coming, isn't he?”
Also, the subject of the tag is always a pronoun.
“Karen bought some new shoes, didn't she?”
“That clock is new, isn't it?”
Tag questions can have two meanings depending on how they are said. If the voice goes up at the end of the tag they are real questions.
“We don't have to go to the meeting, do we?”
“This train is going to stop in Boise, isn't it?”
However, if the voice goes down at the end of the tag, the speaker is only asking the listener to agree with him.
“This movie is really boring, isn't it?”
“Terry doesn't work very hard, does he?”