Premium/discount (gwoeyul, the gap rate) measures how far an ETF's market price has drifted from its net asset value. Tracking error measures how far that NAV has drifted from the underlying index. The two names get lumped together, but they occur in different places: the price gap is baked into your fill the moment an order executes, while tracking error grinds away at returns for as long as you hold.
Regulation has moved to tighten the first one. According to Digital Times, from 19 August 2026 the closing-price gap-rate obligation imposed on brokerage liquidity providers (LPs) narrowed from 3% to 2% for domestic-asset products and from 6% to 5% for overseas-asset products. Wild swings in single-stock leveraged products triggered the rule change.
One hits at execution, the other over the holding period
The formula is simple. KB's financial guide defines the gap rate as (market price − reference price) ÷ reference price × 100. If the reference price is 10,000 won and the ETF trades at 10,100 won, the gap is 1%. That reference price, the NAV, is calculated only once a day between 7pm and 9pm after the close, so intraday you watch iNAV, the exchange's real-time estimate.
LPs are the ones who close that gap, posting two-way quotes near iNAV so the market price cannot wander far from fair value. But there are windows where the quoting obligation is waived: the morning call auction from 08:30 to 09:00, the first five minutes of trading from 09:00 to 09:05, and the closing call auction from 15:20 to 15:30. That is why gaps repeatedly spike right at the open and into the close.
Tracking error is a different animal — not something an LP can fix, but a product of how the fund is run. Full replication versus sampling, the management fee, transaction costs when index constituents change, and the timing of dividend and interest treatment all contribute.
What a 1% gap actually costs you
Expressed as a percentage, the gap looks trivial. Applied to an actual round trip on a 10,000-won ETF, it does not. The table below calculates the round-trip loss for combinations of entry and exit gap rates, assuming the index does not move at all. The final column converts that loss into years of management fees for a low-cost ETF charging 0.05%.
| Gap at purchase | Gap at sale | Buy → sell price (ref. 10,000 won) | Round-trip loss (vs. reference) | Equivalent at a 0.05% fee |
|---|---|---|---|---|
| +0.5% | 0.0% | 10,050 → 10,000 won | 50 won (0.50%) | 10 years |
| +1.0% | 0.0% | 10,100 → 10,000 won | 100 won (1.00%) | 20 years |
| +2.0% | −1.0% | 10,200 → 9,900 won | 300 won (3.00%) | 60 years |
| +4.0% | −2.0% | 10,400 → 9,800 won | 600 won (6.00%) | 120 years |
The third row is what happens when you enter near the old domestic limit of 3% and exit on the opposite side. The index has not budged, yet 3% has left the account. The fourth row corresponds to the 4% domestic threshold that now starts the caution-designation process under the revised rules.
People who agonise over 0.01 percentage points of fees are often numb to a 1% price gap. The first bleeds out over a year; the second is gone the instant you are filled.
What the tighter 2% limit really changes
The more consequential change is speed, not the number. Financial News reports that once the gap exceeds twice the management limit, a pre-designation notice is issued; if it breaches that level again within 10 trading days, the product is designated a caution issue immediately. That threshold is 4% for domestic-asset products and 10% for overseas ones. The designation process itself was shortened from three steps to two.
A designated issue trades under single-price auction for three trading days. Continuous matching stops and fills occur only at set intervals, which makes exiting at a chosen moment difficult — liquidity, not the loss itself, becomes the first problem.
The same revision raised the entry bar for single-stock leveraged products. Retail investors must now hold a 30 million won cash deposit, complete three hours of prior education, and additionally clear at least five trading days and five hours of simulated trading.
Where tracking error opens up, and the delisting line
Tracking error is a selection-stage number. When several ETFs follow the same index, comparing headline fees is not enough; what matters is how closely actual NAV returns tracked the index. Products following overseas indices accumulate error through FX timing and foreign market holidays in particular.
The exchange does not let that relationship break indefinitely. The Kodex investment guide from Samsung Asset Management explains that if the correlation coefficient between the daily change in NAV per unit and the daily change in the underlying index falls below 0.9 for three consecutive months, it becomes grounds for delisting. So does losing every LP and failing to sign a replacement within one month, or having trust principal and total net assets stay below 5 billion won through the following half-year end.
What to watch
- The gap right before you order — put iNAV and the current price side by side. The LP obligation lines are 2% for domestic-asset products and 5% for overseas ones.
- The time of day you trade — 08:30–09:00, 09:00–09:05 and 15:20–15:30 are the windows where LP quoting is waived.
- Caution-issue notices — 4% domestic and 10% overseas start the process; designation means three trading days of single-price auction.
- Total net assets — below 5 billion won through the following half-year end is a delisting ground. Check smaller products first.
- The spread between NAV return and index return — compare same-index products on this, not on headline fees.
This framework has a clear failure condition. In heavily traded large-cap index ETFs with a functioning LP, the gap typically stays inside 0.1%, which makes the arithmetic above look like an overblown worry. In thin thematic or leveraged products, the third row of the table is not an exception but a routine scene.