The Commissioner, or any person authorized in writing by the Commissioner, is authorized to enter into an agreement in writing with any person relating to the liability of such person (or of another person for whom such person acts) with respect to any tax imposed under this chapter for any taxable period. Such agreement shall be final and conclusive, and, except upon a showing of fraud or malfeasance or misrepresentation of a material fact:
5 Del. C. § 1809