Many contracts allow for an early separation under certain conditions, and this letter explains that a contractor or freelancer will be exercising their out clause.
It is with regret that I must exercise the out clause of my contract with XYZ Company.
As required, this letter shall serve as notice that my last day will occur at the end of the number of weeks specified. You will note that no penalties are stipulated in my contract, but I am aware that I will forfeit a percentage of my bonus.
Please rest assured that I have no interest in disparaging the reputation of XYZ Company. I just simply must move on at this time.