The basic path: open an account, choose a fund, and invest

To invest in an S&P 500 index fund, you need a brokerage account — a place where you can buy and sell investments. You open one online with a brokerage firm (Vanguard, Fidelity, and Charles Schwab are the largest), link a bank account, transfer money in, search for an S&P 500 fund by name or ticker symbol, and place a buy order. The whole process takes about 15 minutes once your account is open and funded. The fund then holds your money in a basket of 500 large U.S. company stocks, automatically rebalanced to match the index.

The hardest part for most people is not the mechanics — it is choosing which brokerage and which specific S&P 500 fund to use, because the names are similar and the differences matter over decades. This guide walks you through both decisions in order.

Key Takeaways

  • You must open a brokerage account with a firm like Vanguard, Fidelity, or Charles Schwab before you can buy any fund.
  • Different S&P 500 funds charge different annual fees (called expense ratios), ranging from 0.03% to 0.20%, which compound into thousands of dollars over 30 years.
  • The three largest S&P 500 funds are VOO (Vanguard), IVV (BlackRock), and SPY (State Street), and all three track the same index with nearly identical results.
  • You can invest a lump sum or set up automatic monthly deposits, and both approaches work equally well over long periods.
  • Once you buy the fund, you do not need to do anything — the fund automatically reinvests dividends and rebalances itself.

Step 1: Choose a brokerage and open an account

A brokerage is a company that lets you buy and sell investments. The major ones are Vanguard, Fidelity, Charles Schwab, E-Trade, and TD Ameritrade. All of them let you open an account online for free, with no minimum deposit required (though some funds have a $1,000 or $3,000 minimum for the first purchase). The account takes 5 to 10 minutes to set up — you provide your name, Social Security number, address, and employment status, and the brokerage verifies your identity when ready.

The choice between brokerages matters less than you might think. All of them offer S&P 500 index funds with low fees, and all of them have mobile apps and customer service. Pick the one whose website feels clearest to you, or stick with whichever one your bank uses (many banks own brokerages). Vanguard is the largest S&P 500 fund provider and is owned by its investors rather than shareholders, which some people prefer. Fidelity and Schwab are equally solid and slightly easier for beginners to navigate.

Step 2: Link your bank account and transfer money

Once your brokerage account is open, you need to move money into it. You do this by linking your checking or savings account and initiating a transfer. The brokerage will ask for your bank's routing number and your account number (both visible on a check or in your bank's app). The transfer usually takes 1 to 3 business days. You can transfer as little as $1, though most S&P 500 funds require a minimum first purchase of $1,000 to $3,000.

Some brokerages let you set up automatic monthly transfers, which is useful if you plan to invest regularly. Others require you to initiate each transfer manually. Check your brokerage's website for the option before you fund the account the first time.

Step 3: Search for and select an S&P 500 fund

Once money is in your account, log in and look for a search box or a "buy" button. Type the name or ticker symbol of an S&P 500 fund. The three largest are:

  • VOO (Vanguard S&P 500 ETF) — expense ratio 0.03%
  • IVV (iShares Core S&P 500 ETF) — expense ratio 0.03%
  • SPY (SPDR S&P 500 ETF Trust) — expense ratio 0.09%

All three track the same 500 companies and produce nearly identical returns. The difference is the annual fee: VOO and IVV charge 0.03% per year, meaning you pay $3 per year for every $10,000 invested. SPY charges 0.09%, or $9 per $10,000. Over 30 years, that difference compounds into thousands of dollars, so VOO or IVV is the better choice for most people. If your brokerage does not offer one of these, ask which S&P 500 fund it does offer and check the expense ratio — anything under 0.20% is reasonable.

If you opened your account at Vanguard, you may also see mutual fund versions of these funds (like VFIAX instead of VOO). Both versions track the same index and have the same fee. The ETF versions (VOO, IVV, SPY) are slightly simpler for beginners because you buy them like a stock — one share at a time — rather than in dollar amounts. Either works.

Step 4: Place your buy order

Click on the fund name and you will see a screen asking how much you want to buy. If you are buying an ETF like VOO, you enter the number of shares (for example, 10 shares). If you are buying a mutual fund, you enter a dollar amount (for example, $5,000). The brokerage will show you the current price and the total cost before you confirm. Review it, then click "buy" or "confirm order."

The order executes when ready during market hours (9:30 a.m. to 4 p.m. Eastern Time on weekdays). If you place an order after market close or on a weekend, it will execute at the next market open. You will see the purchase appear in your account within seconds, and the fund shares will be yours when ready.

Step 5: Set up automatic reinvestment and do nothing else

S&P 500 funds pay dividends — small cash payments from the companies in the fund — usually four times a year. Your brokerage account has a setting called DRIP (dividend reinvestment plan) that automatically uses those dividends to buy more shares of the fund. Turn this on in your account settings. It costs nothing and means your investment grows without you having to do anything.

After that, you are done. Do not check the balance daily or try to time the market. Do not sell when the market drops — that is when the fund is cheapest, and selling locks in losses. If you have money left over each month, set up automatic monthly transfers and let them buy more shares automatically. The fund itself rebalances to stay aligned with the S&P 500 index, so you do not need to rebalance manually.

What happens if you use a retirement account instead

If you are investing through a 401(k) at work or an IRA (Individual Retirement Account), the process is slightly different but the end result is the same. A 401(k) usually offers a limited menu of S&P 500 funds — often just one or two. Pick whichever one is available and has the lowest expense ratio. An IRA (whether traditional or Roth) works like a regular brokerage account: you open it, fund it, search for an S&P 500 fund, and buy it. The main difference is that money in an IRA grows tax-deferred or tax-free, depending on the type, so you should prioritize funding an IRA before a regular brokerage account if you have the choice.

The annual contribution limits are $7,000 for an IRA (as of 2024, though this varies by year) and varies for a 401(k) depending on your employer's plan. A regular brokerage account has no contribution limit, so you can invest as much as you want once you have maxed out retirement accounts.

Frequently Asked Questions

Do I have to invest a large amount to start?

No. Most S&P 500 funds have a minimum first purchase of $1,000 to $3,000, but some brokerages (like Fidelity and Schwab) have no minimum. After the first purchase, you can add as little as $1 at a time. Many people start with $1,000 and then add $100 or $500 monthly.

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

They track the same index and have the same annual fee. The main difference is how you buy them: ETFs (like VOO) are bought by share count, like a stock, while mutual funds (like VFIAX) are bought by dollar amount. For beginners, ETFs are slightly simpler because the price is clearer. Both are equally good long-term investments.

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

Theoretically, yes — if all 500 companies in the index went to zero, the fund would be worthless. In practice, this has never happened in U.S. history. The S&P 500 has recovered from every major crash, including the Great Depression, 2008 financial crisis, and 2020 pandemic crash. If you are investing for 20+ years, historical data shows the fund has always gained value over that period.

Should I invest a lump sum or spread it out over months?

Both work equally well over decades. Lump sum investing puts your money to work when ready and historically has slightly higher average returns. Dollar-cost averaging (investing the same amount monthly) feels less risky psychologically because you buy at different prices. Pick whichever approach you will actually stick with — consistency matters more than timing.

Do I need to file taxes on S&P 500 fund investments?

Yes, but only on gains and dividends. If you hold the fund in a regular brokerage account for more than one year before selling, you pay long-term capital gains tax (lower than ordinary income tax). Dividends are taxed as ordinary income in the year you receive them. If the fund is in a 401(k) or traditional IRA, you pay no tax until you withdraw. If it is in a Roth IRA, you pay no tax ever. Your brokerage sends you a tax form (1099) each January listing your gains and dividends.