Dear Sunu,
Before embarking on this, have you specified the project-related employment terms to your employee? Assuming you have tied up your employee with project-related employment.
Dear Mr./Ms. XXXX,
This letter is to inform you of the termination of your services to our organization as the project XXXXX, for which you were recruited, has been completed, and we no longer require your services (as stated in the Appointment Order or Contract). We thank you for your service and appreciate your contribution to the project. We will reach out to you if your services are needed in the future. We wish you all the best in your future endeavors.
Best regards,