I actually know quite a few idioms and other phrases for completion already as I am a native speaker. I am just wonder if there are any examples that relate to something that is formal such as an event. EXAMPLES: Round out, wrap up, finish out, finish up, sum up, end of the road, come to an end, tail end, end of the line, and let out.
: to finish something appropriately: The couple topped off the romantic evening with a walk along the river. The American Heritage® Dictionary of Phrasal Verbs
: to end or terminate something (with something). They topped the building off with a tall flagpole. McGraw-Hill Dictionary of American Idioms and Phrasal Verbs
: to bring something to a finish; end something: We need to wind up this project before January. This card game is fun, but let's wind it up before dinner.`The American Heritage® Dictionary of Phrasal Verbs
: to end or cause something to end gradually The storm finally began to wind down after four hours of heavy rain. We wound down our affairs in Europe and left for home. Cambridge Dictionary of American Idioms
Perhaps you could modify "It's not over until the fat lady sings" in such a way that says it is over.
For example: "That's it! We can go home now! The fat lady just sang."
Wikipedia: "It ain't over till (or until) the fat lady sings (emphasis added) is a colloquialism and has been classified as a proverb. It means that one should not presume to know the outcome of an event which is still in progress. More specifically, the phrase is used when a situation is (or appears to be) nearing its conclusion. It cautions against assuming that the current state of an event is irreversible and clearly determines how or when the event will end. The phrase is most commonly used in association with organized competitions, particularly sports.
"The phrase is generally understood to be referencing the stereotypically overweight sopranos of the opera...."
One idiomatic expression meaning "It's finished" that has emerged in the past decade or so is "Stick a fork in it; it's done." The original sense of the phrase was "It's ready to take out of the oven or off the grill because it's fully cooked." In the context of sports, politics, and business, the phrase is sometimes used to suggest that something is hopelessly lost. From Will Meyerhofer, Way Worse Than Being a Dentist: The Lawyer's Quest for Meaning (2011):
There's slow at the office. Then there's moribund. Like, stick a fork in it, parrot in the Monty Python skit, no longer viable, kaput, over and out, flatlining...dead dead dead.
But it continues to be used in positive settings as well. From Debbie Stoller, Stich 'n Bitch: The Knitter's Handbook (2003):
You probably won't believe this, but when you come back to it, about twenty-four hours later, your piece will actually be the shape that you blocked it to. It will be perfect, and even, and lovely. Stick a fork in it, baby, because it's done.
From Allan Wolf, Immersed in Verse (2006):
Revising Your Poems
I can almost hear your groan at the very mention of this despicable "revising" word Teachers say it a lot, and they seem to say it just when you're feeling so proud of your perfectly perfect, finished final- draft, stick-a-fork-in-it-'cause-it's-done poem.
From Gigi Gates, I Made It (2013):
When you decide to allow God to order your steps in all you do it is when the devil will attempt to attack you at all turns. We have to have faith to know when we forgive then it is done—I mean you can stick a fork in it because it is done, never to be brought up again. Bottom line forgiving is not for the other oerson it is to free you up so God can move you to another level in His Word.
From Robert Gifford, Research Methods for Environmental Psychology (2015):
The values of χ2 and its associated df [degrees of freedom] express the heterogeneity of the data used to test a comparison. If the ci [confidence interval] does not include 0.0 and if this χ2 is significant, the interpretation is that there is a solid overall finding for the claim in question but there is also a lot of variety in the data and so further, more focused research would probably be worth doing. If the respective ci does not include 0 and respective χ2 is not significant, more detailed work would probably not be worth doing. Stick a fork in it: it's done. Move on to another topic that is not already so firmly established.