You buy index funds through a brokerage account by opening an account with a broker, depositing money, and placing an order for the fund or ETF you want

The actual purchase takes minutes once your account is set up and funded. You log into your brokerage account, search for the index fund by its ticker symbol or name, choose how many shares you want, and click buy. The broker executes the trade and the fund appears in your account. The longer part is choosing which broker to use and which index fund to buy — not the transaction itself.

You do not need permission from anyone, a financial advisor, or a government agency to buy an index fund. You need only a brokerage account, money to invest, and a decision about which fund matches your goals. This guide walks you through each step and the choices you will face.

Key Takeaways

  • A brokerage account is straightforward a container where you hold investments; you open one online with a broker like Fidelity, Vanguard, Charles Schwab, or a discount broker, and it takes 10 to 20 minutes.
  • You can buy index funds as mutual funds (which you buy once per day at the closing price) or as ETFs (which trade throughout the day like stocks), and both track the same underlying indexes.
  • The purchase itself happens in your brokerage account by searching for the fund's ticker symbol, entering the number of shares, and clicking buy.
  • Most brokers charge no commission to buy index funds, though some mutual funds have a sales load (a percentage fee) that you should check before buying.
  • You can buy index funds in a regular taxable account, a retirement account like an IRA, or a 401(k) if your employer's plan offers index fund options.

Choosing a broker and opening an account

A broker is a company that holds your money and executes trades on your behalf. You do not need to use the same broker as your friends or family — the choice depends on what features matter to you and how much money you plan to invest.

The major brokers used by individual investors are Fidelity, Vanguard, Charles Schwab, E-Trade, and Merrill Edge. Discount brokers like Robinhood, Webull, and M1 Finance also exist and charge lower or no fees, though they may have fewer research tools or educational resources. All of them allow you to buy index funds with no commission.

To open an account, you visit the broker's website, click the button to open a new account, and answer questions about your name, address, Social Security number, employment, and investment experience. The broker verifies your identity and usually approves you within a few minutes to a few hours. You then link a bank account so you can transfer money into the brokerage account. This entire process takes 10 to 20 minutes online.

Understanding mutual funds versus ETFs

Both mutual funds and ETFs are index funds — they both track an index and hold the same stocks or bonds. The difference is how they trade and when you see the price.

A mutual fund is priced once per day, after the market closes at 4 p.m. Eastern time. You place an order to buy during the day, but you do not know the exact price until that evening. You buy whole shares or fractional shares (a portion of a share). Most index mutual funds have no commission and no sales load, though you should check the fund's prospectus to confirm.

An ETF (exchange-traded fund) trades throughout the market day like a stock. The price changes every few seconds. You can see the price before you buy and you can place an order at any time the market is open. You can also set a limit order (buy only if the price drops to a certain level). Most brokers now allow you to buy fractional shares of ETFs as well, so you do not need a large amount of money to start.

For a beginning investor, the choice between the two matters less than the choice of which index to track. Both are low-cost ways to own a diversified portfolio. ETFs are slightly more tax-efficient in taxable accounts, but the difference is small for most investors.

Finding and selecting the right index fund

Index funds are named after the index they track. A fund that tracks the S&P 500 will have "S&P 500" in its name. A fund that tracks the total U.S. stock market will say "total market" or "total stock market." A fund that tracks international stocks will say "international" or "emerging markets."

Each index fund has a ticker symbol — a short code of letters. The Vanguard S&P 500 ETF is VOO. The Fidelity S&P 500 Index Fund is FXAIX. When you search for a fund in your brokerage account, you search by ticker symbol, not by the fund's full name.

The main thing to compare between similar funds is the expense ratio — the annual fee the fund charges as a percentage of your investment. An S&P 500 index fund at one broker might charge 0.03% per year while another charges 0.10%. On a $10,000 investment, that is $3 per year versus $10 per year. Over decades, the lower-cost fund saves you thousands. Most index funds charge between 0.03% and 0.20% per year. Actively managed funds charge much more (often 0.50% to 1.50%), which is why index funds are popular.

You can compare funds side by side on your broker's website before you buy. Most brokers show the expense ratio, the index the fund tracks, and the fund's performance over the past year, five years, and ten years. Performance history does not predict future results, but it shows you whether the fund is tracking its index correctly.

Depositing money and placing your first order

Once your brokerage account is open, you need to transfer money into it. You do this by linking your bank account and initiating a transfer from your bank to the brokerage account. This usually takes one to three business days. Some brokers offer when ready transfers if you connect your bank account through a service like Plaid.

Once the money is in your brokerage account, you are ready to buy. Log into your account, search for the index fund by its ticker symbol, and click on it. The broker shows you the current price (for an ETF) or the price from the last market close (for a mutual fund). You enter the number of shares you want to buy or the dollar amount you want to invest. Most brokers now let you invest any dollar amount, even if it does not divide evenly into whole shares — they buy fractional shares for you.

Review the order one more time to make sure the ticker symbol is correct and the number of shares matches what you intended. Then click the button to confirm the purchase. The order is executed when ready (for an ETF) or at the market close that day (for a mutual fund). The fund now appears in your account and you own it.

Tax considerations and account types

You can buy index funds in three types of accounts: a regular taxable brokerage account, a retirement account like a traditional or Roth IRA, or a 401(k) if your employer offers index fund options.

In a taxable account, you pay capital gains tax when you sell the fund at a profit. You also pay tax on any dividends the fund distributes. Index funds are tax-efficient because they trade less frequently than actively managed funds, so you owe less in taxes each year.

In a traditional IRA or Roth IRA, you do not pay tax on gains or dividends while the money is in the account. You pay tax later (traditional IRA) or never (Roth IRA). Most people find that buying index funds in a retirement account is the best use of that account because index funds are already tax-efficient and the account's tax shelter is wasted on them.

In a 401(k), your employer may offer a selection of index funds as investment options. You choose which funds to invest your contributions in when you enroll in the plan. The same rules explore — no tax on gains or dividends while the money is in the account.

Common mistakes to avoid when buying index funds

The most common mistake is buying an actively managed fund by accident. Search results sometimes show both index and non-index funds with similar names. Check the expense ratio and the fund's description to confirm it is an index fund that tracks a specific index, not a fund that tries to beat the market.

Another mistake is buying multiple funds that track the same index. If you own both VOO (Vanguard S&P 500 ETF) and IVV (iShares Core S&P 500 ETF), you are holding the same 500 companies twice. This is redundant and wastes money on fees. Pick one S&P 500 fund and stick with it.

A third mistake is trying to time the market — waiting for the price to drop before you buy. Index funds are meant to be held for years, and the cost of waiting for a better price usually outweighs any savings. If you have money to invest, invest it. If you are saving money over time, invest it on a regular schedule (monthly or quarterly) regardless of the price.

Finally, do not confuse a low price per share with a good deal. A fund trading at $50 per share is not cheaper than a fund trading at $150 per share if they track the same index. The price per share depends on how the fund is structured, not on its quality. Compare expense ratios and the index tracked, not the share price.

Frequently Asked Questions

Do I need a lot of money to start buying index funds?

No. Most brokers now allow fractional share purchases, so you can invest any amount — $10, $100, or $1,000 — without waiting to save up for a whole share. Some brokers have no minimum account balance. Start with whatever amount you can afford and add to it over time.

Can I buy index funds directly from the fund company instead of through a broker?

Yes, Vanguard and Fidelity allow you to open an account directly with them and buy their own index funds without using a separate broker. This is simpler if you plan to buy only that company's funds. If you want to compare funds from multiple companies, using a broker that offers all of them is easier.

What happens if the broker I choose goes out of business?

Your investments are protected by the Securities Investor Protection Corporation (SIPC), which guarantees up to $500,000 per account if a broker fails. Your index funds remain yours and are transferred to another broker. This is extremely rare — major brokers are heavily regulated and have been operating for decades.

Should I buy index funds in a taxable account or a retirement account?

If you have access to a 401(k) or IRA, prioritize those first because the tax shelter is valuable. Once you have maxed out your retirement account contributions (the limits change each year), buy index funds in a taxable account. Index funds are tax-efficient, so the taxable account is not a bad place for them.

Can I set up automatic purchases of index funds each month?

Yes. Most brokers offer automatic investment plans where you set up a recurring transfer from your bank account and choose which fund to buy each month. This removes the decision of when to buy and is a straightforward way to invest consistently over time.