What an S&P 500 index fund is

An S&P 500 index fund is a fund that holds the same 500 stocks that make up the S&P 500 index. The S&P 500 is a list of 500 large U.S. companies maintained by Standard & Poor's, a financial data company. When you own shares in an S&P 500 index fund, you own a small piece of all 500 companies at once, rather than picking individual stocks yourself.

The fund's value rises and falls with the index. If the 500 companies in the index gain value overall, your fund gains value. If they lose value, your fund loses value. You do not need to decide which companies to buy or sell — the fund manager straightforward holds the same companies the index holds, in roughly the same proportions.

S&P 500 index funds exist inside retirement accounts like 401(k)s and IRAs, and also as standalone investments through brokerages. Different companies offer their own versions — Vanguard, Fidelity, and Schwab all run S&P 500 index funds with slightly different names and fee structures.

Key Takeaways

  • An S&P 500 index fund holds all 500 companies in the S&P 500 index, so you own a piece of each one with a single investment.
  • The fund's performance matches the index's performance minus the fund's annual fee, which is typically between 0.03% and 0.20% per year.
  • You can buy S&P 500 index funds through a 401(k), an IRA, or a regular brokerage account, depending on your situation and tax goals.
  • The 500 companies in the index change over time as companies grow, shrink, or merge, but the fund automatically adjusts to match those changes.

Which companies are in the S&P 500

The S&P 500 includes large U.S. companies across many industries: technology (Apple, Microsoft, Nvidia), finance (JPMorgan Chase, Bank of America), retail (Amazon, Walmart), healthcare (Johnson & Johnson, UnitedHealth), energy, manufacturing, and others. The list is not fixed — Standard & Poor's adds and removes companies based on size, trading volume, and other factors.

The largest companies in the index make up a bigger portion of the fund's value than smaller ones. Apple, Microsoft, and Nvidia, for example, represent a larger share of the fund than a smaller company would. This means your fund's performance is influenced more by what the biggest companies do than by what smaller ones do.

You can see the full current list of 500 companies on the S&P Dow Jones Indices website, which Standard & Poor's maintains. The list updates whenever a company is added or removed.

How fees work in S&P 500 index funds

Every S&P 500 index fund charges an annual fee, called an expense ratio, which is a percentage of the money you have invested. This fee pays for the fund manager to maintain the fund and keep it aligned with the index. The expense ratio is deducted automatically from your fund's value each year.

Different providers charge different fees. Vanguard's S&P 500 ETF charges around 0.03% per year. Fidelity's S&P 500 index fund charges around 0.015% per year. Other funds charge 0.10% to 0.20% or higher. Over decades, even a small difference in fees adds up — a 0.10% fee costs you more money than a 0.03% fee on the same investment over 30 years.

When you see a fund's historical return listed, that return already includes the fee. So if a fund returned 10% in a year and charges 0.05% annually, the fund itself gained 10.05% before the fee was subtracted.

Tax treatment of S&P 500 index funds in different accounts

Where you hold an S&P 500 index fund determines how taxes work. Inside a 401(k), you do not pay taxes on gains until you withdraw money in retirement. Inside a traditional IRA, the same rule applies. Inside a Roth IRA, you pay no taxes on gains ever, as long as you follow withdrawal rules.

In a regular taxable brokerage account, you pay taxes each year on dividends the fund receives from the 500 companies, and you pay capital gains taxes when you sell shares for a profit. Index funds are tax-efficient compared to actively managed funds because they trade less often, which means fewer taxable events.

If you are deciding between holding an S&P 500 fund in a retirement account versus a taxable account, the tax treatment is usually the main difference. The fund itself works the same way in both places.

How S&P 500 index funds compare to actively managed stock funds

An actively managed stock fund has a manager who picks individual stocks they think will outperform the market. An S&P 500 index fund straightforward holds the 500 stocks in the index and does not try to beat the market — it tries to match it.

Actively managed funds typically charge higher fees (often 0.50% to 1.50% or more per year) because they pay a manager to research and pick stocks. S&P 500 index funds charge lower fees because there is less work involved. Over long periods, the lower fees of index funds often result in better returns than actively managed funds, even though the actively managed fund is trying to outperform.

Some investors prefer index funds for simplicity and lower cost. Others prefer actively managed funds because they believe a skilled manager can beat the market. Both approaches exist, and both are available in retirement accounts and taxable accounts.

How to buy an S&P 500 index fund

If your employer offers a 401(k), you can usually choose an S&P 500 index fund from a list of investment options. You select it during enrollment or during the annual open enrollment period, and money from your paycheck is invested in it automatically.

If you have an IRA, you open an account with a brokerage (Vanguard, Fidelity, Schwab, or another firm) and buy shares of an S&P 500 index fund the same way you would buy any other fund. You can set up automatic monthly contributions if you want.

In a taxable brokerage account, the process is the same as an IRA — you open an account with a brokerage and buy shares. You can buy as much or as little as you want, whenever you want, with no contribution limits.

Different brokerages offer different S&P 500 index funds. Some offer mutual funds (which you buy by dollar amount), and some offer ETFs (exchange-traded funds, which you buy by share count). Both track the S&P 500, but they have slightly different mechanics. Your brokerage's website will show you which S&P 500 funds it offers and their fees.

How the index changes over time

The S&P 500 is not a permanent list. Standard & Poor's removes companies that no longer meet size or trading requirements, and adds new ones that do. When a company is removed, the fund automatically sells it and buys the replacement. When a company is added, the fund automatically buys it.

These changes happen a few times per year on average. Your fund manager handles the buying and selling automatically — you do not need to do anything. The fund stays aligned with the index without any action on your part.

Over decades, the companies in the index have changed significantly. Technology companies make up a much larger share now than they did 20 years ago. This shift happens naturally as the economy changes and companies grow or shrink.

Frequently Asked Questions

Can I lose all my money in an S&P 500 index fund?

You can lose money if the 500 companies in the index lose value overall, which happens during market downturns. However, it is extremely unlikely you would lose everything — that would require all 500 large U.S. companies to fail at the same time, which has never happened. Historical data shows that the S&P 500 has recovered from every downturn in its history.

What is the difference between an S&P 500 index fund and an S&P 500 ETF?

Both hold the same 500 stocks and track the same index. The main difference is how you buy them. A mutual fund is priced once per day, and you buy it by dollar amount. An ETF trades throughout the day like a stock, and you buy it by share count. Fees are often similar. Both work inside retirement accounts and taxable accounts.

Do I get dividends from an S&P 500 index fund?

Yes. The 500 companies pay dividends, and the fund passes those dividends to you. In a retirement account, dividends are automatically reinvested. In a taxable account, you can choose to reinvest them or receive them as cash, depending on your brokerage.

How often should I check my S&P 500 index fund balance?

There is no set rule. Some investors check monthly, others check yearly or less often. Frequent checking can lead to emotional decisions during market swings. Many investors set up automatic contributions and check their balance only once or twice a year.

Can I hold an S&P 500 index fund in both a 401(k) and an IRA?

Yes. You can hold S&P 500 index funds in a 401(k), a traditional IRA, a Roth IRA, and a taxable brokerage account all at the same time. Each account has different contribution limits and tax rules, so holding the same fund in multiple accounts is a common strategy.