No, issuance of the Diploma Supplement is mandatory and unofficial, even if the graduate does not have additional information to include in it (article 2, paragraph 1 of Ordinance No. 30/2008). You should refer to IPVC Regulation No. 621/2011.
Issuance of the Diploma Supplement is mandatory and free of charge whenever a diploma is conferred.
In Portugal, following the commitments made within the framework of the Bologna Process, Decree-law No. 42/2005 of February 22 was published. It approved the regulatory principles for the instruments used to develop European Higher Education, particularly with regard to the Diploma Supplement, essentially applying as of 2006-2007.
On January 10, 2008, Ordinance No. 30/2008 was published, which regulates article 39 of Decree-law No. 42/2005.