ETFs vs Mutual Funds: Only One Difference Costs You

The first tax form I ever got genuinely angry about reported a capital gain on a fund I had not sold a single share of. I had bought it, held it, added to it, and at no point taken a dollar out. The form said I owed tax on a gain, and the form was correct.

That form is the one real difference between a mutual fund and an ETF, and everything else people argue about is smaller.

Same basket, two containers

A mutual fund and an ETF, which stands for exchange traded fund, are both pooled vehicles. You give them money, they hold a portfolio, you own a slice of the portfolio.

The same firm will frequently run both versions of the identical strategy, tracking the identical index, holding the identical companies at the identical weights, often managed by the same people on the same desk. If you line up the holdings pages side by side they match.

So this is a question about the container.

Difference one: when you get your price

A mutual fund prices once a day. Put an order in at 10am and you get the price calculated after the market closes, and so does everyone who ordered at 2pm.

An ETF trades all day, so you get whatever the market is asking at the second your order fills, and there is a small gap between the buying price and the selling price called the spread. On a widely traded broad index ETF that spread is usually a cent or two on a share worth a few hundred dollars.

For someone buying once a month and holding for twenty years, this difference is almost meaningless. It matters to people who trade, and if you are buying an index fund you are not trying to be one of them.

Difference two: how you actually put money in

This one is practical and it decides more real cases than the tax argument does. Mutual funds are built for a dollar amount. You say $500 and you get $500 worth, including the fraction of a share.

ETFs are built for share counts, and whether you can buy $500 worth depends on whether your brokerage supports fractional shares and automatic recurring purchases. Plenty do now. Plenty of workplace plans still do not offer ETFs at all.

If the wrapper you pick is the one you will not actually fund every month, you picked wrong regardless of the tax argument.

Difference three: the form I got angry about

A mutual fund has to sell holdings sometimes, either because the index changed or because other shareholders redeemed and the fund needed cash to pay them. When it sells at a profit it realises a capital gain, and the law requires it to pass that gain through to everyone who holds the fund on a particular date.

You get the gain whether you sold or not. You get it whether you bought last month or ten years ago. If another investor's exit forced the sale, you get their gain.

The arithmetic is not trivial in a bad year. A 5% capital gains distribution on a $50,000 holding is $2,500 of taxable gain. At a 15% long-term rate that is $375 owed, on a year you took nothing out.

ETFs mostly sidestep this. Large institutions create and redeem ETF shares by swapping baskets of the actual underlying stocks rather than cash, and handing over securities instead of selling them does not trigger a gain inside the fund. Broad index ETFs therefore go year after year distributing no capital gains at all.

The two things that do not differ

Dividends. Both wrappers pass through whatever the underlying companies pay, and in a taxable account both are income to you in the year you receive them, reinvested or not.

Cost. There is no rule saying an ETF is cheaper.

The expense ratio is set by the fund company, and for the same index at the same firm the two versions are frequently within a hundredth of a percentage point of each other. On $50,000, a hundredth of a point is $5 a year.

So the cheap-against-expensive argument people attach to this question is usually an argument about index funds against actively managed funds, wearing a different coat.

One ETF quirk worth knowing

Because an ETF trades on an exchange, its price can drift a little away from the value of what it holds. Buying at a premium means paying slightly more than the basket is worth, and selling at a discount means taking slightly less.

On a large, heavily traded fund holding US stocks that drift is a rounding error, because institutions arbitrage it away within seconds. It widens in thinly traded funds, in funds holding assets that trade in a different time zone, and in the first and last few minutes of the session. Avoid the open and the close and most of it stops applying to you.

One practical constraint on top of all this. Most workplace retirement plans offer mutual funds and not ETFs, so inside a 401k the decision is usually made for you.

What to check tonight

Pull up each fund you hold in a taxable brokerage account and look at whether it is a mutual fund or an ETF. The name usually gives it away, and the fund page always does.

Then look at the distributions history on that fund page, which lists what it has paid out and in what form. Dividends are one line. Capital gain distributions are a separate line, and a fund that shows several years of them in a row is telling you something about the years ahead.

If you find a mutual fund throwing off gains in a taxable account, the fix is not automatically to sell it, because selling is itself a taxable event and may cost more than the problem. Start by pointing new money at the ETF version and let the old position sit. That decision is free.