ETF NAV vs market price: premiums, discounts and which one your data shows

An ETF has two prices: the net asset value (NAV), which is the value of the fund's holdings minus liabilities divided by shares outstanding and is struck once a day, and the market price, which is whatever the shares last traded at on an exchange during the day. When the market price is above NAV the ETF trades at a premium; below, at a discount. For liquid ETFs on open markets the two stay within a few basis points because authorised participants can create or redeem shares whenever they diverge, but they can separate when the underlying market is closed, illiquid or stressed. Factsheet and API performance figures are calculated from NAV, not from the market price.

What NAV is

The NAV of a fund is the total value of its assets less its liabilities. NAV per share is that figure divided by the number of shares in issue. For a UCITS ETF the administrator computes it once per dealing day, after the markets where the fund invests have closed, using the closing prices of every holding and the day's exchange rates, minus accrued fees. It is the price at which the fund itself issues and redeems shares with authorised participants, and it is the price series that a fund's total-return figures are built on.

NAV has three properties that matter for data:

• It is daily, so a NAV series has one point per dealing day (weekends and holidays have none).
• It is in the share-class currency, which is why a USD share class and a EUR-hedged share class of the same fund have different NAV series.
• It is net of ongoing charges, because fees accrue inside the fund before the NAV is struck. Returns computed from NAV are therefore net of the TER.

What the market price is

An ETF share is listed on one or more exchanges and trades like a stock. The market price is the last traded price, and the bid and ask around it are quoted by market makers. During the trading day exchanges and data vendors also publish an indicative NAV (iNAV), an estimate of the NAV updated every few seconds from live prices of the holdings, so that traders can see whether the quote is fair. The official NAV, however, only exists at the end of the day.

Because trading happens on the exchange and not with the fund, the market price is set by supply and demand for the ETF shares, and nothing forces it to equal NAV at every instant. What keeps it close is arbitrage.

Creation and redemption: why the gap stays small

Authorised participants (large broker-dealers) can deliver a basket of the underlying securities (or cash) to the fund and receive new ETF shares at NAV, or return ETF shares and receive the basket. If the ETF trades at a premium, an AP buys the basket, creates shares at NAV and sells them on the exchange at the higher price, pushing the price back down; at a discount the trade runs the other way. For an ETF whose holdings are liquid and trading at the same time as the ETF, this keeps premiums and discounts to a few basis points, roughly the cost of doing the arbitrage.

When premiums and discounts appear

The first row is the one that confuses most readers. An MSCI World ETF listed in Frankfurt prices all day, but its US holdings, which are the majority of the index, only trade from the afternoon European time. Morning "premiums" and "discounts" in that ETF are mostly the market pricing in the US futures move since the previous close, not a mispricing. In these cases the market price is arguably the more current number, and the NAV catches up in the evening.

Which price your data shows

Factsheets and regulatory documents use NAV. So does FundFacts API: the performance block is computed from the issuer's published NAV history when there is one, using the last NAV of each month, and otherwise from the returns stated in the factsheet. That means:

• cumulativePerformance, indexedPerformance.points, calendarReturns and annualisedReturns are NAV-based total returns in the share-class currency.
• headlineMetrics.volatility3y, headlineMetrics.sharpe3y and metrics.maxDrawdown are computed from the same monthly NAV returns over the trailing three years.
• dataAsOf is the date of the latest NAV observation used, or the factsheet's reporting date.
• There is no market price, bid/ask or premium/discount field. Those are exchange data, vary by listing (one ISIN, several exchanges), and are not part of a factsheet.

This is the right basis for comparing funds, because NAV returns depend only on the portfolio and the fees, not on which exchange or time of day an investor traded. It is not, however, what any individual investor earned: their return is market price to market price, and the difference from the NAV return is the premium at purchase minus the premium at sale, plus the spread paid. Over long holding periods in liquid ETFs that difference is small; over a day in a stressed bond ETF it can be the whole story.

Reading the NAV-based figures

typescript
const r = await fetch("https://fundfactsapi.com/api/v1/funds/IE00B3RBWM25", {
  headers: { Authorization: "Bearer ffk_live_..." },
});
const { data } = await r.json();
​
// Monthly NAV-based series, rebased to 100 at the first point
const series = data.indexedPerformance.points;          // [{ date: "2021-09", fund: 100, index: null }, …]
const last = series.at(-1);
console.log(last.date, last.fund);                        // e.g. "2026-08", 168.2
​
// Annualised NAV total returns
for (const row of data.annualisedReturns) console.log(row.label, row.fund, row.index);
​
// The date these figures refer to
console.log(data.dataAsOf);                               // latest NAV observation used

If you also display live market prices from an exchange feed, label the two clearly: "NAV return" for the factsheet figures and "price" for the quote, and show the premium/discount as its own number computed from the day's official NAV once it is published. Mixing a live price into a NAV series produces a last point that is not comparable with the rest.

NAV, premium and tracking

Premium and discount are about the ETF's share price versus its own NAV. Tracking difference is about the ETF's NAV versus its index. Both are usually small for a liquid physical ETF, and both are worth separating from the third source of divergence, which is the replication method. A reader who sees an ETF "underperforming" should ask which of the three gaps they are looking at before drawing a conclusion. The performance data post describes the NAV-based series in detail, and the field reference lists every performance key.

For non-ETF UCITS funds none of this applies: there is no exchange and no market price, and investors deal directly with the fund at NAV (sometimes adjusted by swing pricing).