none of your business!

none of (one's) business

Something that is of no concern to another. It's really none of his business what I do with the money I earn.
See also: business, none, of
Farlex Dictionary of Idioms.

(It's) none of your business!

It is nothing that you need to know. It is none of your concern. (Not very polite.) Alice: How much does a little diamond like that cost? Mary: None of your business! John: Do you want to go out with me Friday night? Mary: Sorry, I don't think so. John: Well, what are you doing then? Mary: None of your business!
See also: none, of
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • none of (one's) business
  • none of business
  • none of one's business
  • like nobody’s business
  • like nobody's business
  • How's business?
  • business woman
  • go about (one's) business
  • go about your business
  • open for business
References in periodicals archive
None of your business! It's none of your business!'.
The truth, the whole truth and nothing but the truth? It's none of your business!
Grandmother Schafer, visiting on this auspicious occasion and rocking in a rocking chair, asked, "Well, David, what does a physiologist do, anyway?" When he answered, "Grandma, a physiologist studies the parts of the body and tries to find out how they work," the rocking stopped and this good Christian lady drew herself up, looked him straight in the eye, and said, "Why, David, that's none of your business!"
If someone wanted to study our thoughts, many of us would respond, "Why, that's none of your business!"
Humanist Values, Brain Science, and "Mind-Reading"