Under Article 50 of the Contract of Employment Act and Article 13(1) of the Working Hours Act, employers may seek exemption from fixed working hours in respect of employees who occupy managerial or supervisory posts or positions of trust. The possibility of such exemption was recently extended to employees whose jobs comprise preparatory or complementary operations which by their nature can only be performed outside normal working hours, and to employees who regularly do their work outside the establishment, away from the immediate control of the management (Decree-Law No. 398 of October 16, 1991). Such exemption must be requested by the employer and becomes effective only with prior authorization from the Ministry of Employment and Social Security, and always subject to the agreement of the employee concerned. Such employees are entitled to a special allowance which must not be less than the sum corresponding to one hour's overtime per day, unless collectively agreed otherwise. This entitlement to a special allowance may be relinquished by employees occupying managerial posts

http://www.eurofound.europa.eu/emire/PORTUGAL/EXEMPTIONFROMF...