When I ask my children to do chores, they often say they will do them under a condition like giving them some money or cake or letting them watch TV, etc.
How do we tell someone we want them to do what we say without any negotiation?
For example, "You have to do it. No deal!" or something like that!
You have to do it, period8.
which means no further discussion is possible or desirable.
One possibility is
And that's that!
or
And that's final!
which mean "and that is all there is to say about it; there will not be any more discussion."
Reference: https://www.ihbristol.com/content/and-thats-thatand-thats-final
A phrase that covers this, and also means "no excuses", is
No ifs, ands, or buts!
The more literal meaning being "no responses with the word 'if', etc."
"No deal" works great to say "no" to what they've already proposed. If you want instead to say "no" to what you expect them to ask for, "no deals" would be better.
You could say, no bargaining, please, but if you're speaking to your kids, I don't see why you couldn't say no deal! You could also go for
That's not negotiable!
The technical term non-negotiable is described by Cambridge in this way:
Something that is non-negotiable cannot be changed by discussion.
I'm not asking you to X. I'm telling you to X.
is a reasonably typical way to do respond to an attempted negotiation where I am.
In a more shorthand: I'm not asking, I'm telling. Or even I'm not asking.
This is what my parents used to say to me:
You are going to do your homework and I don't want to hear any more about it!
or
... and I don't want to hear another word about it!
So, basically, you are saying that you are having the final word, and no longer wish to discuss the matter further (with the argumentative party).
Another variation on the theme:
... and it's not up for (any further) discussion/debate!
or
... and I'm not discussing it any further!
You seem to be asking about an order that’s not to be questioned. There are many ways to express this, with some of the most direct (suitable for a parent talking to their child) being “Now!” or “Go!”
One more suitable for adults would be, “This isn’t open for discussion,” or “This decision is final.” One associated with the military would be, “That’s an order,” or “You have your orders.”
An idiom for when you present a non-negotiable offer is, take it or leave it.
Some people might find:
“I need you to do X”
to be sufficiently firm.
(It's a phrasing that seems to have gained in popularity. I'd take it to be a very firm instruction — though I get the impression that other folks might find it much softer.)
There are a number of ways to communicate the idea you're trying to express, depending on how forceful you're trying to be and what your relationship is with the other person. One way is with an implied threat of consequences.
You have to do it, or else.
The "or else" implies that there will be unspecified consequences or an escalation if it (whatever "it" is) is not done. In American English, you might hear this phrase between parents and children (usually with the implied threat of consequences), managers and employees (same), or even coworkers or young siblings (where the implied threat is most often escalation to an authority figure).
Note that while there are some contexts where the phrase could mean the consequences are external or impartial (e.g. "Don't forget to finish your term paper, or else!") as a general rule you should be aware that the phrase is both intentionally vague and will generally be perceived as a direct or indirect threat. It should therefore be used cautiously, and should typically not be used in polite, formal, or professional speech or writing.
There are better alternatives for effective communication about both essential requirements and known consequences. Implied threats and vagueness provide neither, but this phrase does pop up fairly often in informal and colloquial speech.
This is not a negotiation.
cannot be beat for conveying that you are not open to negotiating, and it is sometimes used in exactly the kind of situation you describe, albeit usually in response to the kind of bargaining attempt you mention.
You might emphasize by following up with
Do it!
and even
Now!
The appropriate imperative depends on the hierarchical authority of your relationship.
God to man: Thou shalt, thou shalt not
Parent to child: you must, you must not (if English, mustn't)
Employer to employee: xyz, do you understand me?
Military: and THAT's an Order!
Peer to Peer: Lets xyz, will you comply?
Pastor to flock: these are not the "ten Suggestions"
Of course facial expression and body language either reinforce a command, or soften the urgency.
