Early voting is an election system by which eligible voters cast their ballots prior to an election. Early voting kicked off at the sixth local election on June 4, 2014, two years after early voting was first introduced in 2012 and was implemented in two by-elections in 2013. Since the introduction of early voting, the proportion of early voting turnout compared to the overall turnout has gradually increased. The proportion was 20% at the introduction of early voting and now exceeds 30%.

 Election by overseas residents is an election system that allows overseas Koreans to exercise their right to vote. In 2007, the Constitutional Court made a constitutional decision on the right to vote for overseas Koreans, and election by overseas residents was introduced in 2009. This system was first implemented in the 19th National Assembly Election on April 11, 2012. Currently, this system is implemented in Presidential Elections and National Assembly Elections, but not in local elections, re-elections, and by-elections. In the 20th National Assembly Election, 198 polling stations were installed in 169 Korean overseas facilities, including Embassies, Consulate Generals, Consulates, and Consular Offices. Of the estimated 1.98 million overseas voters, 152,217 voters registered. Among them, 63,797 voted, representing a 41.4% turnout.