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How an ETF actually works under the hood

Part of ETF basics

An ETF trades like a share all day, yet somehow its price stays glued to the value of the hundreds of things it owns. There’s a clever bit of machinery making that happen — and it’s worth a look.

The problem an ETF solves

Say you want to own a slice of hundreds of companies at once, buy or sell it any time the market is open, and always at a price that’s fair — not wildly above or below what those companies are actually worth. Buying all the shares yourself would be impossible for most people. An ETF is the wrapper that makes it a single, tradable thing. The interesting question is: how does its price stay honest?

The creation-and-redemption trick

Here’s the machinery. A handful of large firms (‘authorised participants’) are allowed to hand the fund a basket of the real underlying shares and get brand-new ETF units in return — or do the reverse, handing back units to get the shares. If the ETF ever trades a touch above what its holdings are worth, they create more units and sell them, nudging the price back down; if it trades below, they do the opposite. This constant, profit-seeking tug keeps the ETF’s price glued to the value of what it owns.

The creation-and-redemption loop, stage by stage

  1. Basket in

    An authorised participant (AP) — a large trading firm with a direct agreement with the fund provider — assembles a basket of the exact underlying shares the ETF is supposed to hold, and delivers them to the provider.

  2. New units out

    In exchange for the basket, the fund issues a block of brand-new ETF units to the AP. No cash changes hands at this stage: shares in, units out.

  3. Price snaps back

    The AP sells the new units in the market. If the ETF had been trading above what its holdings were worth, the extra supply nudges the price back down. The same logic runs in reverse when the ETF trades at a discount — the AP buys units and hands them back, getting the underlying shares and pocketing the price difference.

The value of everything a fund holds, divided by the number of units, is its NAV (net asset value) — the ‘true’ worth per unit. The market price can sit slightly above NAV (a premium) or below it (a discount). For big, popular funds holding easy-to-trade shares, that gap is usually tiny thanks to the mechanism above. It can widen for funds holding hard-to-trade things, or when a market the fund covers is closed — a reason very niche ETFs deserve a closer look.

You never get a fee invoice. The provider takes its cut — the The yearly running cost of the fund, shown as a % of your money. Lower is cheaper. More → — by skimming a tiny fraction of the fund’s assets each day, so the price you see already has the fee baked in. Some providers earn a little extra by lending the fund’s shares to other investors for a fee, which can quietly offset costs (and adds a small risk). None of this is a separate charge you pay by hand — it’s all inside the wrapper, which is exactly why a low headline fee matters.

🤔 What keeps an ETF’s market price close to the value of the shares it holds?

Common questions

So how is the fee actually taken from me?
Not as a bill. A tiny slice of the fund’s value is deducted continuously, day by day, so it’s already reflected in the price and performance you see. You never transfer the fee yourself — which is also why it’s easy to overlook, and why comparing fees matters.
Should I worry about premiums and discounts?
For large, broadly held funds tracking liquid markets, the gap to NAV is usually negligible. It’s more worth a glance with niche funds — narrow themes, thinly traded corners, or markets in a different time zone — where the price can stray a little further from the underlying value.