The Catholic Church represents 81% of all believers in Portugal. Other religious groups, like Non-evangelical Protestants, Muslims, Eastern Orthodox Church, Church of Jesus Christ, Christian groups and Jewish, are very small. Portuguese State and Catholic Church has a unique contract under the ‘Concordata’ between Portugal and Vatican that grants several privileges to the Catholic Church and to Catholic institutions. With the object of not losing their rights, smaller faith communities intervene mainly in social work and accept the privileges that Catholic Universe still prevails privileges in Portuguese society.
For more information about the ‘Concordata’ see here: https://www.vatican.va/roman_curia/secretariat_state /archivio/documents/rc_seg-st_19400507_missioni-santa-sede-portogallo_po.html.