Hindi ko sure exactly kung ano lahat ng specific documents required for that transition, but I know a few of us who switched from employed to voluntary and nag-submit kami ng resignation letter, birth certificate, and valid ID sa PhilHealth office mismo, mas mabilis kasing-sigurado kung personal na papunta ka rather than waiting for online stuff dito sa Pilipinas! Best talaga na tawagan mo directly ang PhilHealth hotline or pumunta ka sa nearest branch near you para sure, kasi bawat case minsan may slight difference depende sa situation mo. Good luck sa transition!