put down in black and white
put (something) down in black and white
To write something down as a means of making it official, legitimate, or binding. They promised to give me a raise when the project is complete, but I want them to put it down in black and white first. Make sure you have them put the deal in black and white before you agree to anything. That's a pretty generous offer—care to put it down in black and white?
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
put something down in black and whiteand set something down in black and white
Fig. to write down the terms of an agreement; to draw up a written contract; to put the details of something down on paper. (Alludes to black ink and white paper.) We agree on all the major points. Now, let's set it down in black and white. I think I understand what you are talking about, but we need to put down the details in black and white.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.