Question

you didn't put it back. ( add a question tag)

Answer 1

Didn't you put it back. Did you?

Answer 2

Given sentence:

You did not put it back.

Sentence after adding appropriate question tag:

You didn't put it back, did you?

Additional information:

Question tag may be simply and compactly defined as a single phrase or group of words that is added at the end of a statement or sentence in order to and converts it to a question.

The British English call it "Question Tag" whereas on the other hand American English call it "Tag Question" or "Tail Question".

Question tags are generally common in familiar conversation and not in formal writing or conversation.