You can buy an S&P 500 index fund through a brokerage account in about 15 minutes

An S&P 500 index fund is a fund that holds all 500 companies in the S&P 500 list, so you own a piece of each one with a single purchase. You buy it the same way you buy individual stocks: through a brokerage account (a company that lets you trade investments). The fund tracks the performance of those 500 companies, so when the index goes up or down, your fund does too.

The practical steps are: open a brokerage account, deposit money, search for the fund by its ticker symbol, and click buy. You can do this with as little as $1 at most brokerages, though some have a $500 or $1,000 minimum for the first purchase. The whole process takes longer to think about than to complete.

Key Takeaways

  • S&P 500 index funds come in two main types — mutual funds and exchange-traded funds (ETFs) — and both track the same 500 companies but trade slightly differently.
  • You buy through a brokerage account (Fidelity, Vanguard, Charles Schwab, and others), not directly from the fund company.
  • Each fund charges a fee called an expense ratio, usually between 0.03% and 0.20% per year, which is deducted automatically from your account.
  • You can set up automatic monthly purchases so money moves from your bank account to the fund without you having to remember to buy.

Mutual funds versus ETFs: which type to choose

The two main flavors of S&P 500 index funds are mutual funds and exchange-traded funds (ETFs). Both hold the same 500 stocks and track the same index. The difference is how they trade and when you can buy or sell them.

A mutual fund trades once per day, after the market closes. You place an order during the day, but the price you pay is set at 4 p.m. Eastern time, after all the day's trading is done. An ETF trades throughout the day like a stock — you can buy or sell it at any time the market is open and see the price change in real time. For most people holding long-term, this difference does not matter. ETFs often have slightly lower expense ratios (the annual fee), but mutual funds are simpler if you are setting up automatic monthly purchases.

Popular S&P 500 index funds include Vanguard's VFIAX (mutual fund) and VOO (ETF), Fidelity's FSKAX (mutual fund) and FXAIX (mutual fund), and Schwab's SWTSX (mutual fund). All track the same index and cost between 0.03% and 0.04% per year.

Opening a brokerage account and depositing money

You need a brokerage account to buy any fund. This is a holding account at a company that lets you buy and sell investments. Major brokerages include Fidelity, Vanguard, Charles Schwab, E-Trade, and Robinhood, though there are dozens of others. Most have no account opening fee and no minimum balance to start.

The signup process is online and takes 10 to 15 minutes. You will need your Social Security number, a government ID, your address, and your employment information. The brokerage will ask you to link a bank account so you can transfer money in. Once your account is open and verified (usually the same day or next business day), you can deposit money by transferring it from your bank.

Start with whatever amount you are comfortable with. Many people begin with $500 to $1,000, but you can start smaller. Some brokerages let you buy fractional shares, meaning you can invest $50 or $100 and own a partial share of the fund.

Finding and purchasing the fund

Once money is in your account, log in to your brokerage and look for a "Buy" or "Trade" button. Search for the fund by its ticker symbol — for example, VOO, VFIAX, or FSKAX. The brokerage will show you the current price and let you enter how many shares you want to buy or how much money you want to spend.

If you are buying a mutual fund, place your order during market hours (9:30 a.m. to 4 p.m. Eastern, Monday through Friday). Your order will execute at the closing price that day. If you are buying an ETF, you can place an order anytime, but it will only execute while the market is open. After you click confirm, the shares appear in your account and the money is deducted from your cash balance.

You now own a piece of all 500 companies in the S&P 500. You do not need to do anything else unless you want to buy more.

Understanding expense ratios and annual costs

Every fund charges a fee called an expense ratio, expressed as a percentage of your investment per year. An expense ratio of 0.04% means you pay $4 per year for every $10,000 you have in the fund. This fee is deducted automatically — you never write a check or see a bill. It comes out of the fund's value before your returns are calculated.

S&P 500 index funds are among the cheapest investments available because they simply hold the same 500 stocks in the same proportions. They do not require a manager to pick stocks or make active decisions. Expense ratios typically range from 0.03% to 0.20% depending on the fund and brokerage. Vanguard, Fidelity, and Schwab all offer S&P 500 index funds with ratios below 0.04%.

Over time, a lower expense ratio compounds into real savings. On a $50,000 investment, the difference between a 0.03% ratio and a 0.20% ratio is about $85 per year. Over 30 years, that difference grows significantly. When comparing funds, check the expense ratio first — it is one of the few costs you can control.

Setting up automatic monthly investments

Most brokerages let you set up automatic investments, where a fixed amount of money moves from your bank account to your brokerage account on a schedule you choose, then automatically buys the fund. This is called dollar-cost averaging — you invest the same dollar amount every month regardless of whether the fund price is high or low.

To set this up, go to your brokerage's settings and look for "Automatic Investments," "Recurring Investments," or "Systematic Investment Plan." You will enter the fund's ticker symbol, the dollar amount you want to invest each month, and the day of the month you want it to happen. Most brokerages let you start with as little as $50 per month.

Automatic investing removes emotion from the process. You do not have to decide when to buy or worry about timing the market. The money goes in every month, buys shares at whatever price they are that day, and you build your position over time. You can pause or change the amount anytime.

What happens after you buy: holding and monitoring

After you purchase an S&P 500 index fund, you own it. You do not need to do anything. The fund automatically rebalances itself to stay aligned with the index — when companies are added or removed from the S&P 500, the fund adjusts. You will receive dividends (small cash payments) from the companies in the fund, usually quarterly. Most brokerages automatically reinvest these dividends back into the fund, buying more shares with the payout.

Check your account balance periodically if you want to, but do not check it daily or weekly. The price fluctuates constantly, and frequent checking often leads to panic selling during downturns. Index funds are designed to be held for years or decades. The longer you hold, the more time the compounding works in your favor.

If you need to sell, log into your account, select the fund, and click sell. You can sell all your shares or just some. The sale executes at the next available price (end of day for mutual funds, anytime during market hours for ETFs), and the money goes back into your cash balance. You can then transfer it to your bank account.

Frequently Asked Questions

What is the minimum amount I need to invest to start?

Most brokerages have no minimum to open an account. Many let you buy fractional shares, so you can invest $1, $10, or $100 and own a proportional piece of the fund. Some brokerages have a $500 or $1,000 minimum for the first purchase, but this is becoming less common. Check your chosen brokerage's website for their specific rules.

Do I owe taxes on my S&P 500 index fund?

Yes, but only when you sell shares or receive dividends. If you hold the fund in a regular taxable brokerage account, you owe capital gains tax on any profit when you sell, and income tax on dividends. If you hold it in a tax-advantaged account like a 401(k) or Roth IRA, taxes are deferred or eliminated. Talk to a tax professional about which account type makes sense for your situation.

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

Theoretically, yes, but it would require all 500 of the largest U.S. companies to fail simultaneously, which is extremely unlikely. The S&P 500 has recovered from every major crash in its history. That said, the value will fluctuate — you might see a 20% or 30% drop in a bad year. If you cannot tolerate seeing your money decline temporarily, index funds may not be right for you.

Should I buy a mutual fund or an ETF version of the S&P 500?

For most people, it does not matter much. Both track the same index and have similar low costs. Mutual funds are simpler for automatic monthly investing. ETFs trade throughout the day like stocks, which matters only if you plan to buy and sell frequently. Pick whichever your chosen brokerage makes easiest to use.

What if I want to stop investing or need the money?

You can pause automatic investments anytime through your brokerage settings — no penalty, no notice required. If you need to withdraw money, log in and sell as many shares as you need. The money goes back to your cash balance, and you can transfer it to your bank account within a few business days. There is no early withdrawal penalty like there is with retirement accounts.