none of your business!

It’s really none of his business what I do with the money I earn.

Something that is of no concern to another. It’s really none of his business what I do with the money I earn.

(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!

McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.