The handover cannot happen until the government crafts the mechanism for abdication and Felipe's assumption of power. The proposal is expected to pass quickly because Rajoy's center-right Popular Party has an absolute majority in Parliament.
The 76-year-old king and Felipe, 46, appeared Tuesday at a military ceremony outside Madrid as Rajoy was meeting with his cabinet.
Juan Carlos led Spain's transition from dictatorship to democracy but was hit by damaging scandals amid Spain's financial meltdown.
He announced Monday he was abdicating because his son is ready for the job and Spain needs a "new era of hope."