You are buying 20 shares of our fictional Market Basket ETF. Assume the share price is $10.10 and its basket value is $10 per share at the same instant. You pay $202 for $200 of investments.
The extra $2 goes to the seller. That 1% gap is a reason to check valuation timing and trading conditions. ETF shares have a market price of their own, but institutions can exchange them for the underlying investments. That exchange gives traders a reason to bring the prices closer together.
Start with the price you would pay
Here, NAV means the per-share net asset value quoted on a fund page. A market price above that value is a premium to NAV; a price below it is a discount to NAV.
Here, ($10.10 − $10) ÷ $10 × 100 = 1%.
Official NAV is usually calculated once per business day. A live quote and yesterday's NAV do not measure the same moment. Check both timestamps and whether the markets for the holdings are open. The bid-ask spread adds another clue about trading conditions.
You buy ETF shares from another market participant; your trade does not force the fund to buy stocks.
An authorized participant (AP) is an institution with an agreement to create or redeem large blocks directly with the fund. A creation unit is one such block; its size varies by fund. A market maker quotes buy and sell prices on the exchange, a separate job an AP may also do.
When the ETF trades above its basket
Arbitrage means trying to profit from different prices for matching investments. At $10.10, ETF shares cost more than the basket they represent.
Our example uses 50,000-share creation units. For both directions, hold prices fixed through each trade and leave out trading, financing and fund transaction costs.
The AP buys the basket the fund specifies for 50,000 × $10 = $500,000 and swaps it for 50,000 new ETF shares. This is ETF creation.
Selling at $10.10 leaves $505,000 − $500,000 = $5,000 before costs.
Selling more ETF shares puts downward pressure on their price; buying the basket puts upward pressure on its value. Those pressures tend to narrow the premium. The fund manager does not set the exchange price.
New shares arrive with matching assets. Each extra share brings $10 of investments, so existing investors still have $10 of net assets per share.
When the ETF trades below its basket
At $9.90, ETF shares cost less than their basket. The AP buys 50,000 shares for $495,000 and returns them to the fund for $500,000 of securities. This is ETF redemption: the returned shares are canceled.
Selling the basket leaves $500,000 − $495,000 = $5,000 before costs. Buying ETF shares pushes their price up; selling the released securities pushes the basket's value down. That tends to narrow the discount.
Arbitrage pulls prices together; it does not bolt them together. A gap too small to cover costs gives traders little reason to act. Hard-to-trade holdings, market stress or APs unable or unwilling to trade can leave a bigger gap.
An ETF owning overseas stocks may still trade after their home exchanges close. Its price can reflect news those stocks have not yet traded on. How the fund values those holdings also affects the reported premium or discount. A reported gap need not be a trading opportunity.
Why in-kind exchanges affect US taxes
This tax comparison uses September 2026 US rules: you are a US tax resident holding US-registered funds in a taxable account.
An in-kind exchange delivers securities instead of cash. The tax benefit comes from avoiding a sale: the ETF hands appreciated holdings to the AP without selling them to raise cash and realizing a gain. That helps many ETFs distribute fewer capital gains than comparable mutual funds.
Creation and redemption can also use cash. Cash redemptions and routine portfolio sales can still realize gains. Dividends, distributed gains and gains on your own sale can still have tax consequences. A US listing alone does not determine your tax treatment; your residence and account matter.
Price gaps are not tracking gaps
An ETF can trade exactly at NAV and still lag its index. For an index ETF, tracking difference measures the return gap against the index it follows. Use fund NAV returns so exchange-price premiums do not muddy the comparison.
Both total-return series include reinvested distributions.
Say the fund's NAV total return is 7.92% and the index's is 8.00% over the same year, both in US dollars. Tracking difference is 7.92% − 8.00% = −0.08 percentage points, or −8 basis points.
| Check | What is compared | Time basis |
|---|---|---|
| Premium / discount | Share price and NAV | Matched moment |
| Tracking difference | Fund and index total returns | Same period |
Expenses, trading costs, holding only a sample of the index, cash and trading timing all affect tracking. Income from lending portfolio securities can offset part of the drag.
Operating expenses are already reflected in that gap.
Tracking error measures how much the fund's periodic return gaps vary, rather than the size of the gap over the full period.
For your $202 purchase, the first check is whether the quote and $10 basket value belong to the same moment. For a holding, compare its NAV total return with its own index over identical dates, in the same currency and with matching distribution treatment.
Those checks tell you how closely the ETF follows its basket and index. Next compare broad-market, sector, thematic and factor funds to see how different the baskets themselves can be.
In short
- You trade ETF shares on an exchange; authorized participants exchange large blocks with the fund.
- Creation adds shares; redemption removes them. Both give traders incentives to narrow price gaps.
- Costs and market stress can leave gaps; mismatched valuations can make them look larger.
- In-kind redemptions can reduce US fund capital gains without making your returns tax-free.
- Tracking difference measures a return gap over time; a premium or discount measures a price gap.