Index Funds vs. ETFs: Which to Hold, and Where, in Retirement

The difference is how shares are bought and sold, and that drives the tax result. You buy or sell a mutual fund directly from the fund company at the net asset value computed once a day after the close. You buy or sell an ETF from another investor on an exchange, at a market price during the day, and you pay the bid-ask spread (SEC Investor Bulletin on ETFs). Large institutions called authorized participants create and redeem ETF shares with the fund, usually by exchanging baskets of the underlying securities rather than cash.

For a long-term holder, the trading differences are minor. Broad index ETFs trade with narrow spreads, and a retiree who rebalances once or twice a year is not paying much for intraday pricing. Mutual funds are still more convenient for automatic dollar-amount purchases and withdrawals, and many 401(k) plans offer only mutual funds or collective trusts. Expense ratios on large index funds and their ETF counterparts are close; check each fund's prospectus fee table rather than relying on a headline number.

Because they can get rid of low-basis stock without selling it. When a mutual fund's shareholders redeem, the fund often has to sell holdings for cash, and any net gains it realizes must be distributed to everyone who still owns the fund, including people who never sold. When an ETF faces redemptions, it typically hands the institution a basket of securities in kind, which is not a sale by the fund, so there is no gain to pass on. The SEC notes that because many ETFs buy and sell portfolio securities in kind, they typically make fewer capital-gain distributions than mutual funds (SEC).

For a taxable investor, a distribution is a tax bill you did not choose. Capital-gain distributions are taxed as long-term gains no matter how long you have owned the fund (IRS Publication 550), and they raise adjusted gross income, which feeds Medicare premiums two years later and the taxation of Social Security. For a married couple with modified AGI above $250,000, the 3.8% net investment income tax applies on top (IRS Topic 559).

Put ETFs, or index funds that share a portfolio with an ETF class, in the taxable account; hold whatever is cheapest and most convenient in IRAs and Roths. Inside a traditional IRA, a distribution is not taxed when paid; everything is taxed as ordinary income when it leaves the account. Inside a Roth, qualified withdrawals are tax-free. The ETF's tax advantage has nothing to work on in either.

Asset location goes beyond the wrapper. Assets that throw off ordinary income, such as taxable bonds, REIT funds and actively traded funds, generally belong in the IRA. Broad stock index ETFs, whose income is mostly qualified dividends, belong in the taxable account, where losses can also be harvested and where heirs get a step-up in basis. Our dividend calculator shows what those dividends pay and the tax on them. The Roth, which you will likely spend last or leave to heirs, suits the assets with the highest expected growth.

One caution for this age group: the traditional IRA is also where RMDs come from, and RMDs are figured on the prior December 31 balance. Holding bonds there slows the IRA's growth and so the size of future RMDs, which some retirees welcome and others offset with Roth conversions before RMDs begin. The asset allocation worksheet lays out holdings by account so the overall mix stays where you want it.

Switch freely inside IRAs, where a sale is not taxed. In a taxable account, switch only when it costs little or nothing: through a share-class conversion, when a position has little gain, or when the gain can be absorbed at 0% or by harvested losses. Three routes are available.

1. 1Share-class conversion within the same fund. Most Vanguard funds that offer ETF shares let you convert mutual fund shares into ETF shares of the same fund, and Vanguard says the conversion is tax-free when held at Vanguard (Vanguard). It is one-way: ETF shares cannot be converted back. Fractional mutual fund shares may be sold for cash, which is a small taxable sale.
2. 2Waiting for your fund company to add an ETF class. In November 2025 the SEC granted Dimensional Fund Advisors exemptive relief to offer ETF share classes of its existing mutual funds (Dimensional), and many other managers have filed for the same. If your fund company is on that list, a conversion route may appear without a sale. Read the fund's notice for the tax treatment before acting.
3. 3A whole-fund conversion. Some managers have converted entire mutual funds into ETFs by reorganization. Shareholders receive ETF shares; the fund's proxy or information statement explains the tax treatment. You need a brokerage account, not a fund-company account, to hold the result.

Transfer the account in kind, then rebuild slowly. Most brokerage-to-brokerage moves run through ACATS, which carries positions over as they are, with their cost basis, and involves no sale (FINRA). The receiving firm starts the transfer; you do not need to ask the adviser first, though a courteous note helps with anything that sits outside the brokerage account.

The trap is assets that cannot move. Under FINRA Rule 11870, proprietary products of the old firm, and third-party funds the new firm has no arrangement to hold, may be nontransferable; the firm must tell you which ones and let you choose to liquidate them, leave them where they are, or have them re-registered in your name (FINRA Rule 11870). Ask the new custodian to check the holdings list before you sign, so a forced sale does not surprise you in a year you did not plan for it.

The fee saved is what pays for the patience. At 1% a year, a $2 million account pays $20,000 annually in advisory fees. If you are unsure whether to leave or what a fair alternative looks like, our guide to choosing a fee-only adviser covers flat-fee and hourly planners.

Yes. Most custodians let you move shares from a traditional IRA to a taxable account to satisfy a required minimum distribution. The custodian reports the fair market value on the distribution date as the distribution (IRS Form 1099-R instructions), you owe ordinary income tax on that value as you would on cash, and the shares start life in the taxable account with that value as their basis. RMDs start at 73, or 75 if you were born in 1960 or later.

In-kind RMDs suit people who do not need the money to live on. Walt's IRA held $1.2 million last December 31. His RMD at 75, using the IRS Uniform Lifetime Table divisor of 24.6, is about $48,800 (IRS Publication 590-B). Instead of selling the IRA's bond fund, withdrawing cash and buying a stock ETF in the taxable account, he moves $48,800 of the total-market ETF straight across. No round-trip, no time out of the market, and the taxable account ends up holding the tax-efficient asset.

Three details matter. Withholding must be paid in cash, so leave a little cash in the IRA or pay estimated tax. Distributing an ETF from the IRA shifts your asset location, so rebalance inside the IRA afterward. And if you give to charity, a qualified charitable distribution from the IRA can satisfy the RMD without adding it to income at all. The RMD calculator projects the amounts year by year.

A handful of broad index funds or ETFs at one custodian, with a short written note. The spouse who manages the money is often not the one who outlives the other. Twenty-two positions across four firms, some with an adviser and some in old 401(k)s, is a hard inheritance in a bad month.

Consolidation also sets up the tax outcome. For jointly held taxable assets, the deceased spouse's half generally gets a new basis at death, and in community property states the whole account generally does (IRS Publication 551). After a death is often the best time to clean up a portfolio: positions whose gains were stepped up can be sold for a small tax bill, and the survivor can end up with three funds instead of twenty.

The estate planning basics guide covers beneficiary designations and titling, and our investment portfolio tracker is a simple place to keep the list current.