Korea Exchange after-hours trading sees spike in volatility controls

The Korea Exchange (KRX) initiated its after-hours trading session on September 14, 2026, aiming to enhance global competitiveness and broaden trading opportunities. During the inaugural four-hour session, volatility interruption (VI) mechanisms were activated 1,637 times, a substantial increase from the 400 activations observed during the regular trading day. Excluding simultaneous static and dynamic VI triggers, the figures were 1,112 for after-hours and 391 for regular trading.

The VI mechanism temporarily switches a stock to a single-price auction for approximately two minutes when its price experiences a sharp movement, intended to curb excessive volatility. Market participants attributed the heightened volatility to reduced liquidity, a consequence of the KRX expanding the number of stocks available for after-hours trading to 2,459 from 606 on NXT's after-hours market. Most stocks listed on the Korea Composite Stock Price Index (KOSPI) and KOSDAQ markets were eligible, though exchange-traded funds and notes were excluded due to volatility concerns.

Despite the increased VI activations, the KRX reported that prices were generally stable. The average high-low volatility per stock during after-hours trading was 2.9% for KOSPI stocks and 4.6% for KOSDAQ stocks, which was lower than the 4.1% and 5.8% recorded during regular trading hours, respectively. The exchange stated it applied the same VI thresholds as the regular market to ensure stable operations, acknowledging that after-hours markets typically have lower liquidity and higher volatility.