Is the use of "have eaten" correct in this sentence?

have not

”....you did not eat the chicken before I came back.”

do not

I would either say
“The most important thing is that you have not eaten the chicken before I am back.”
or
“The most important thing is for you to not have eaten the chicken before I am back.”

^ #2 …is for you to not have eaten…

Usually, to form negative infinitives, the not particle is placed before the actual infinitive to have eaten, i.e., not to have eaten, so not to split the infinitive.

If it works for Star Trek, it works for everyone.
To boldly go.

^ If it works for Star Trek, it works for everyone.
Sure! A simple Wikipedia search will tell you so. Usage and catchy phrases have a life of their own. There are more reputable sites that provide a variety of examples though.

Obviously, To boldly go is not a negative statement like in the OP.

This is a case of splitting the infinitive by inserting the adverb boldly to modify the infinitive to go. It is recommended that the adverb be placed in any other part of the sentence to avoid awkward sentences, but this is not written in stone and it sometimes can alter the meaning of your sentence.

.

@Yeahright @kritiper and all the rest

Seems like everyone who has answered missed out on the existence of the subjunctive mood.
Do you agree that this is correct?
It’s important that you not eat the chicken before I am back.
There is no need for an infinitive at all.
Let me make it easier for you to see what I mean.
It’s important that you not HAVE EATEN the chicken before I am back.

So, does HAVE EATEN work in my last sentence?

@Ticce It is grammatically correct but not something one would be likely to say in everyday English. There are less awkward ways to say it. I would probably just say “Please don’t eat the chicken before I come back” but if it is important to you to use the phrase I would say, “It is important that you haven’t eaten the chicken before I come back.” (By the time I come back is better though.)

Disclaimer: I’m not a formal grammarian but a teacher of literature and writing and a user of English for many years.

@janbb
I doubt that “haven’t eaten” is correct. It’s correct in the indicative mood. But we have the subjunctive. I think it should be “not have eaten”.

No it should be have not.

@KRD Would you say “It’s important that you do not do it” or “It’s important that you not do it”?