NTS(National Tax Service) has been trying to pay your Dormant Tax Refund to the bank account of tax payers and it's around 45bil.won as of the end of July 2016.
It.s more than 100,000cases for more than 50,000won refund and total amount is 37bil.won according to the announcement.
These tax refund cash is parking at the NTS account since a lot of tax payers move their address and can't receive the notice letter, or simply ignore it because a lack of time for a small refund even got the notice letter.
Actually you can visit the website(www.hometax.go.kr) and click the "환급금조회" if you already join this website as a taxpayer or click(https://www.hometax.go.kr/websquare/websquare.wq?w2xPath=/ui/pp/index_pp.xml&tmIdx=01&tm2lIdx=0102000000) and type your ARC number.
Even you can just simply visit a near tax office with your ID(driver's license or Alien resident card) and ask them to check whether you have a dormant refund amount, if yes, please ask them pay you immediately by cash.
For warning, NTS never send a text to your mobile for your tax refund, and also never pay you those refund amount through ARS or vending machines, so please be careful if these kind of things happen on your mobile devices.