[entry form 1968+, variant 1909+; by 1837 in the form ''Now you have done it'']
The Dictionary of American Slang, Fourth Edition by Barbara Ann Kipfer, PhD. and Robert L. Chapman, Ph.D. Copyright (C) 2007 by HarperCollins Publishers. Cite This Source
Idioms and Phrases with that does it
that does it
Also,that does the trick. The last requirement has been fulfilled; that accomplishes it. For example, That does it; we're ready to send in the application now, or That last screw does the trick—it's fully assembled. Grose's Dictionary of the Vulgar Tongue (1823) defines do the trick as “accomplish a robbery or other business successfully,” and presumably the it in the first term stands for the trick.
[ Early 1800s