The basic steps to invest in an S&P 500 index fund

You buy an S&P 500 index fund through a brokerage account — an online platform where you can hold and trade investments. Open an account with a brokerage (Fidelity, Vanguard, Charles Schwab, and Robinhood are common choices), link a bank account, transfer money in, search for the fund by its ticker symbol, and place an order to buy shares. The whole process takes about 15 minutes once your account is open and funded.

The fund itself is a collection of 500 large U.S. company stocks bundled together. When you buy shares of the fund, you own a tiny piece of all 500 companies at once. You do not pick individual stocks — the fund manager handles that, and the fund automatically rebalances to stay aligned with the S&P 500 index.

Settlement happens in two business days, meaning your money leaves your bank account immediately but the shares officially appear in your account on day two. You can sell anytime during market hours (9:30 a.m. to 4 p.m. Eastern, Monday through Friday), though most people buy and hold for years.

Key Takeaways

  • You need a brokerage account to buy an S&P 500 index fund; opening one takes 10 to 15 minutes and requires a Social Security number, address, and bank account information.
  • The fund's ticker symbol (SPY, VOO, or IVV are the most common) is how you search for it in your brokerage platform.
  • You can start with any amount, though some brokerages have account minimums ranging from zero to a few thousand dollars.
  • Buying happens during market hours; orders placed after 4 p.m. Eastern execute the next trading day at that day's closing price.
  • The fund charges a small annual fee (called an expense ratio) that ranges from 0.03% to 0.20% depending on which fund you choose.

Choosing a brokerage and opening an account

The brokerage is the middleman between you and the stock market. Most major brokerages charge no commission to buy index funds, so the main differences are the user interface, customer service quality, and which specific S&P 500 funds they offer. Fidelity, Vanguard, and Charles Schwab are known for low fees and strong customer support. Robinhood and M1 Finance appeal to people who want a simpler, mobile-first experience.

To open an account, you will need your Social Security number, a valid ID, your current address, and access to a bank account for transfers. The application is online and takes about 10 minutes. Some brokerages offer a choice between a taxable brokerage account (which you can withdraw from anytime) or a retirement account like an IRA (which has tax advantages but withdrawal restrictions). For most people starting out, a regular taxable account is the simplest choice.

After your account is approved, you link your bank account and transfer money in. This transfer typically takes one to three business days. Once the money is in your brokerage account, it sits as cash and is ready to invest.

Finding and buying the right S&P 500 fund

The S&P 500 index itself is not a fund you can buy directly — it is a list of 500 companies. Multiple fund companies have created their own S&P 500 index funds that track this list. The three most common are Vanguard's VOO, Fidelity's FSKAX, and iShares' IVV. Each holds the same 500 stocks and performs nearly identically, but they charge slightly different fees and may have different account minimums.

Search for the fund by its ticker symbol in your brokerage's search bar. The platform will show you the fund's name, current price per share, and expense ratio (the annual fee). Read the fund details to confirm it tracks the S&P 500 — some similar-sounding funds track different indexes or include international stocks. Once you have found the fund you want, click "Buy" or "Trade," enter the number of shares you want to purchase (or the dollar amount), and review the order before submitting.

Your order executes at the market close price on that trading day if you place it during market hours, or at the next day's close if you place it after 4 p.m. Eastern or on a weekend. You will see the shares in your account two business days later, though most brokerages show them immediately for informational purposes.

Understanding fees and expense ratios

The expense ratio is an annual percentage fee charged by the fund company for managing the fund. For S&P 500 index funds, this is typically between 0.03% and 0.20% per year. On a $10,000 investment, that ranges from $3 to $20 annually. The fee is deducted automatically from the fund's value, so you do not see a bill — it simply reduces your returns slightly each year.

Vanguard's VOO charges 0.03%, Fidelity's FSKAX charges 0.015%, and iShares' IVV charges 0.03%. These differences are small but compound over decades. A difference of 0.05% per year on a $100,000 investment is $50 annually, which adds up. Most brokerages charge no commission to buy or sell index funds, so the expense ratio is the main cost you will encounter.

Some brokerages also offer their own house-brand S&P 500 funds with very low fees. Fidelity's FSKAX and Schwab's SWTSX both charge 0.015% or less. If you are opening an account specifically to invest in an S&P 500 fund, comparing the expense ratios of the funds available at each brokerage is worth a few minutes of research.

Dollar-cost averaging versus lump-sum investing

Dollar-cost averaging means investing a fixed amount on a regular schedule — for example, $500 every month — regardless of the fund's price. Lump-sum investing means putting all your money in at once. Research shows that lump-sum investing performs slightly better on average over long periods, because you are in the market longer. However, dollar-cost averaging can feel less risky psychologically and works better if you are adding to your investment gradually from paychecks.

Most people use a combination: they invest a lump sum when they open the account, then add money monthly or quarterly as they save. Many brokerages offer automatic investing, where you set up a recurring transfer from your bank account and an automatic purchase of the fund on a specific date each month. This removes the decision-making and ensures you stay consistent.

The most important factor is starting early and staying invested through market ups and downs. Whether you invest $5,000 all at once or $500 per month for 10 months matters far less than whether you stay invested for 10 or 20 years.

Tax considerations for index fund investing

In a regular taxable brokerage account, you owe capital gains tax when you sell shares for a profit. If you hold the fund for more than one year before selling, you pay long-term capital gains tax, which is lower than short-term rates. You also owe tax on any dividends the fund distributes (usually once per year), even if you reinvest them. Most S&P 500 index funds automatically reinvest dividends, so you do not have to do anything, but the tax bill still comes due.

If you are investing for retirement, consider opening a Roth IRA or traditional IRA instead of a taxable account. In a Roth IRA, you pay no tax on gains or withdrawals in retirement (though contributions are made with after-tax dollars). In a traditional IRA, contributions may be tax-deductible and you pay tax only when you withdraw in retirement. Both have annual contribution limits (currently $7,000 for people under 50), but they offer significant tax advantages for long-term investing.

If your employer offers a 401(k) with an S&P 500 index fund option, that is often the best place to start, because contributions reduce your taxable income and many employers match a percentage of your contribution.

What happens after you buy

Once you own shares, you do not have to do anything. The fund automatically rebalances to stay aligned with the S&P 500 index, and dividends are reinvested. You can check your account balance anytime, but most successful index fund investors check infrequently — quarterly or annually — to avoid the temptation to buy or sell based on short-term market movements.

If you want to add more money, you simply transfer it to your brokerage account and buy more shares using the same process. If you need to withdraw money, you sell shares (which takes two business days to settle) and transfer the cash back to your bank account. There are no penalties for withdrawals from a taxable account, though selling at a loss means you cannot use that loss to offset other gains.

The fund will send you a tax statement each January showing your dividends and any capital gains from sales. If you held the fund all year and did not sell, you will only owe tax on the dividends.

Frequently Asked Questions

Can I start investing with a small amount of money?

Yes. Most brokerages have no account minimum and allow you to buy fractional shares, meaning you can invest $50 or $100 and own a proportional piece of the fund. Some brokerages like Fidelity and Vanguard have no minimum at all. A few older brokerages still require $1,000 to $3,000 to open an account, but these are becoming rare.

What is the difference between an ETF and a mutual fund version of the S&P 500?

Both track the same index and charge similar fees. ETFs (like VOO or IVV) trade like stocks during market hours and settle in one day. Mutual funds (like FSKAX) trade only at the market close and settle in two days. For most people, the difference does not matter. ETFs are slightly more tax-efficient in taxable accounts, while mutual funds are simpler for automatic investing.

Should I wait for the market to drop before investing?

Timing the market is difficult and most people who try end up worse off. If you have money to invest and a long time horizon (5+ years), investing now is usually better than waiting. Market drops happen regularly, and trying to catch the exact bottom often means missing the recovery. Dollar-cost averaging removes this worry by spreading your investment over time.

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

Extremely unlikely. The S&P 500 would have to drop to zero, which would require all 500 large U.S. companies to fail simultaneously. The index has recovered from every major crash in history. You can lose money if you sell during a downturn, but if you hold long enough, historical returns are positive. Past performance does not may provide future results, but the 90-year track record is strong.

Do I need to rebalance my S&P 500 fund holdings?

No. The fund itself rebalances automatically to stay aligned with the index. You do not have to do anything. If you own multiple different investments (stocks, bonds, real estate), you may want to rebalance that overall portfolio annually, but a single S&P 500 fund requires no action from you.