Extensions of stay may be granted to foreign nationals who enter Portugal on valid short-stay visas or visa waiver/temporary visas/residence visas and seek to remain and extend their visa in Portugal territory for a period longer than originally permitted (visa renewal).
Schengen Visa holders:
Holders of a Schengen visa from any Schengen country who apply for a visa extension in Portugal must provide evidence of a valid reason. Visa extensions are limited to 90 days, and can be extended for an additional 90 days.