(1) When it is difficult to calculate work hours provided by an employee because he or she performs all or part of his or her duty outside the workplace owing to a business trip or any other reason, it shall be deemed that he or she has worked for contractual work hours: Provided, That where it is ordinarily necessary for the employee to work in excess of contractual work hours in order to perform the said duty, it shall be deemed that he or she has worked for the hours ordinarily required to perform that duty.
(2) Notwithstanding the proviso of paragraph (1), where there exists a written agreement between an employer and the representative of employees in regard to the work concerned, the hours as determined by such a written agreement shall be regarded as those ordinarily required to perform the relevant duty.
(3) In case of works designated by Presidential Decree as those which, in light of the characteristics of works, require leaving the methods of performance to an employee' discretion, it shall be deemed that the works have been provided for such work hours as determined by a written agreement between the employer and the representative of employees. In such cases, such written agreement shall specify the matters falling under the following subparagraphs:
1. Work to be provided subject to such written agreement;
2. Statement that the employer would not give specific directions to the employee regarding how to perform the work, how to allocate work hours, etc.;
3. Statement that the calculation of work hours shall be governed by the written agreement concerned.
(4) Matters necessary for implementing paragraphs (1) and (3) shall be prescribed by Presidential Decree.