What an ETF expense ratio really pays for

An exchange-traded fund's expense ratio is stated as an annual percentage of assets, but it is never invoiced. The fund accrues it daily against net asset value, so the cost appears silently as a small drag on performance. Nothing leaves your account; the fund is simply worth marginally less than the index it tracks.

What the ratio covers

• Investment management and index licensing fees.
• Custody, fund accounting and transfer agency.
• Audit, legal and regulatory filing costs.
• Marketing or distribution charges where they apply.

It does not cover the commission your broker charges, the spread you pay when trading, currency conversion, or taxes. Those sit outside the fund and are borne by the investor at the point of transaction.

The costs that hide outside the ratio

Bid-ask spread

Every ETF trade crosses a spread between the best bid and the best offer. For a large, heavily traded fund the spread can be negligible; for a thinly traded niche product it can exceed a year of management fees in a single round trip. Frequent traders should weight spread more heavily than the expense ratio.

Premium and discount to NAV

An ETF's market price can drift from the value of its underlying holdings. Authorised participants arbitrage that gap, but the mechanism works less smoothly when underlying markets are closed or stressed. Fund providers publish historical premium and discount data.

Comparing like for like

In Europe, the key information document states an 'ongoing charges figure' plus separate transaction costs. In the United States, the prospectus fee table states the gross and net expense ratio, where 'net' may reflect a temporary fee waiver that can expire. Read which of the two you are being quoted before concluding that one fund is cheaper.