"You could not have done it without me."
Translation:Du kunne ikke have klaret det uden mig.
You need to know if it is a dependent or indepedent clause. If it is a depedent clause (like this sentence), 'ikke' has to be between the verb and the subject. If it is an indepedent clause, 'ikke' has to be after the verb and the subject.
Example: "Han er IKKE smuk" - "Han er sød, fordi han IKKE er smuk"