[DigitalToday reporter Ji-young Lee (이지영)] COFIX, the cost of funds index that serves as a benchmark for banks’ floating-rate loans, rose across the board for September. The new loans-based COFIX rose 0.25 percentage points in a month to 3.43 percent. If the rise in COFIX is reflected in lending rates, interest burdens for floating-rate mortgage borrowers could increase.

The Korea Federation of Banks said in its “COFIX for September 2026” disclosure released on Wednesday that the new loans-based COFIX rose 0.25 percentage points from the previous month’s 3.18 percent to 3.43 percent.

The new loans-based COFIX posted 3.05 percent in June, 3.18 percent in July and 3.18 percent in August, before widening its increase in September. Compared with 2.52 percent in September last year, it was up 0.91 percentage points in a year.

The balance-based COFIX also rose 0.10 percentage points to 3.15 percent from 3.05 percent a month earlier. The new balance-based COFIX rose 0.08 percentage points to 2.79 percent from 2.71 percent.

With all three indices rising, the trend of increasing funding costs for banks appears to be continuing.

COFIX is the weighted average interest rate of funds raised by eight South Korean banks. It reflects changes in interest rates on major deposit products such as time deposits, installment savings and bank debentures.

The new loans-based COFIX is calculated from funds newly raised in the relevant month, so it reflects changes in market interest rates relatively quickly. By contrast, the balance-based and new balance-based COFIX include existing funding, so rate changes are reflected more gradually.

Short-term COFIX has also been trending higher recently. Short-term COFIX, which was 3.16 percent on Sept. 30, rose to 3.32 percent on Oct. 8 and 3.43 percent on Oct. 14.