Fourteen out of every 100 banknotes in circulation are virtually unusable due to damage, such as tears or stains.
According to the Bank of Korea on Thursday, some 86 percent of banknotes in the country remained in use as of the end of August, while the other 14 percent were withheld from the public because they were in such poor condition.
Almost all of the nation's W50,000 (US$1=W1,187) notes are still in use as they are mostly intact. And about 80 percent of the W10,000 bills, which are only slightly older than the higher-denomination bills, are good enough to stay in circulation.
But the rate of damaged W5,000 is astonishingly high, with 45 percent deemed unfit for use. The equivalent rate for the W1,000 bills is 13 percent.
"Small-denomination notes are more likely to have been damaged because they were issued earlier than higher-denomination bills and they are used more frequently," the Bank of Korea said. "People's habits also play a role."
Scribbles and stains accounted for most of the damage, or 81 percent. Washing and bleaching made up 6 percent, while tearing occurred in 2 percent of cases.