1
general::
Also, that takes care of that. There's no more to be said or done; the matter is finished, the issue is settled. For example, Dad's not buying you a television set, and that's that, or We've paid all we owe, and that takes care of that. [Early 1800s]
American Heritage Idioms
2
general::
Phrase(s): That’s that!
Inf. That is the end of that! Nothing more can be done. • Tom: Well, that’s that! I can do no more. Sally: That’s the way it goes. • Doctor (finishing an operation): That’s that! Would you close for me, Sue? Sue: Nice job, Doctor. Yes, I’ll close.
McGrawhill's American Idioms And Phrasal Verbs