; and (IV) shall cover matters relating to confidentiality, intellectual property rights, and such other matters as the Secretary considers appropriate. (ii) Liability An amount for which an employee is liable under subparagraph (i)(II) shall be treated as a debt due the United States. (iii) Waiver The Secretary may waive, in whole or in part, collection of a debt described in subparagraph (B) based on a determination that the collection would be against equity and good conscience and not in the best interests of the United States, after taking into account any indication of fraud, misrepresentation, fault, or lack of good faith on the part of the employee. (D) Termination An assignment under this subsection may, at any time and for any reason, be terminated by the Department or the private-sector organization concerned. (E) Duration (i) In general Except as provided in subparagraph (B), an assignment under this subsection shall be for a period of not less than 3 months and not more than 2 years, and renewable up to a total of 4 years. (ii) Exception An assignment under this subsection may be for a period in excess of 2 years, but not more than 4 years, if the Secretary determines that the assignment is necessary to meet critical mission or program requirements. (iii) Limitation No employee of the Department may be assigned under this subsection for more than a total of 4 years inclusive of all assignments. (F) Status of Federal employees assigned to private-sector organizations (i) In general An employee of the Department who is assigned to a private-sector organization under this subsection shall be considered, during the period of assignment, to be on detail to a regular work assignment in the Department for all purposes. (ii) Written agreement The written agreement established under paragraph (3) shall address the specific terms and conditions related to the continued status of the employee as a Federal employee. (iii) Certification In establishing a temporary assignment of an employee of the Department to a