You need a brokerage account to buy index funds

An index fund is a mutual fund or exchange-traded fund (ETF) that tracks a market index — a preset list of stocks or bonds. To buy one, you open an account with a brokerage firm, deposit money, and place an order for the fund you want. The brokerage holds the fund in your account and handles the paperwork.

You cannot buy index funds directly from the fund company itself. You buy them through a brokerage — a financial firm licensed to buy and sell securities on your behalf. Common brokerages include Fidelity, Charles Schwab, E*TRADE, Vanguard, and TD Ameritrade. Some are also fund companies (Vanguard runs its own brokerage), but most are separate firms.

The process takes about 10 to 15 minutes to set up, and you can start buying within a day or two once your account is funded.

Key Takeaways

  • You open a brokerage account online, provide your Social Security number and basic personal information, and link a bank account to deposit money.
  • Once your deposit clears — usually one to three business days — you can search for and buy index funds by their ticker symbol or fund name.
  • Index funds come as mutual funds (you buy them once per day at the closing price) or ETFs (you buy them throughout the day like stocks).
  • Most brokerages charge no commission to buy index funds, though some mutual funds carry a small fee paid to the fund company, not the brokerage.
  • You can hold index funds in a regular taxable account or in a tax-advantaged account like an IRA or 401(k), depending on what the brokerage offers.

Choose a brokerage and open an account

Start by picking a brokerage. Look for one that offers the index funds you want to buy, has low or no account minimums, and charges no commission on trades. Most major brokerages meet all three criteria. Read the account opening page to see what information they need — typically your name, address, Social Security number, employment status, and annual income.

Open the account online. The brokerage will ask you to create a username and password, confirm your identity (usually by answering security questions or uploading a photo ID), and choose what type of account you want. A taxable brokerage account is the simplest: you can buy and sell whenever you want, but you pay taxes on gains and dividends each year. An IRA (Individual Retirement Account) or 401(k) offers tax breaks but has rules about when you can withdraw money. If you are unsure which to open, start with a taxable account.

The account opens when ready, but you cannot trade until you fund it.

Link your bank account and deposit money

Once your brokerage account is open, go to the "Deposit" or "Fund Account" section and link your checking or savings account. The brokerage will ask for your bank's routing number and your account number — both appear on a check or in your bank's app. Some brokerages verify the link by making two small deposits to your bank account; you then confirm the amounts in the brokerage app.

After your bank account is linked, you can transfer money to the brokerage. Transfers usually take one to three business days to clear. Some brokerages offer faster options (same-day or next-day) for a small fee, but the standard transfer is free. You do not have to deposit a large amount — many brokerages let you start with $1 or $100, though some index funds themselves have minimums of $500 or $1,000 if you are buying a mutual fund directly.

Once the money appears in your brokerage account, you are ready to buy.

Search for the index fund you want

Index funds are identified by a ticker symbol — a short code like SPY, VOO, or VTI. If you know which fund you want, search for it by ticker in your brokerage's search bar. If you are not sure, you can search by what the fund tracks: "S&P 500 index fund" or "total bond market index fund." The brokerage will show you all available options.

When you find a fund, click on it to see its details: the expense ratio (the annual fee, usually between 0.03% and 0.20% for index funds), the holdings (what stocks or bonds it owns), and whether it is a mutual fund or an ETF. Read the fund's description to confirm it tracks the index you want. For example, the Vanguard S&P 500 ETF (ticker VOO) tracks the S&P 500 index, which includes 500 large U.S. companies.

Do not worry if you see multiple funds that track the same index. They all do the same job; the differences are usually small fees and minor variations in which exact stocks they hold.

Place your order and confirm the purchase

Click "Buy" on the fund page. The brokerage will ask how many shares you want to buy. If you are buying a mutual fund, you can enter a dollar amount (for example, $500) and the brokerage will calculate how many shares that buys. If you are buying an ETF, you enter the number of shares. ETFs trade throughout the day like stocks, so the price changes minute to minute. Mutual funds trade once per day at the closing price, so you see the exact price only after the market closes.

Review the order details: the fund name, the number of shares, the price per share, and the total cost. Confirm that everything is correct, then click "Submit" or "Place Order." The order goes through when ready for ETFs (during market hours) or at the market close for mutual funds. You will receive a confirmation email with the order details and a confirmation number.

The fund now appears in your account holdings. You own it, and any dividends it pays will be deposited into your account automatically.

Understand the difference between mutual funds and ETFs

Both mutual funds and ETFs are index funds, but they work slightly differently. A mutual fund is priced once per day after the market closes at 4 p.m. Eastern time. You place an order during the day, but you do not know the exact price until after the market closes. You can only buy or sell once per day. Most mutual funds have no commission, though some charge a small fee called a load.

An ETF (exchange-traded fund) trades throughout the day like a stock. You see the price in real time and can buy or sell whenever the market is open. ETFs usually have no commission and no load. The trade executes when ready at the price you see. For most people starting out, ETFs are simpler because you know the exact price before you buy.

Both types track an index the same way and have similar expense ratios. The choice between them is mostly about convenience. If you want to buy and forget, either works. If you like to see prices in real time, an ETF may feel more natural.

Know what happens after you buy

Once you own an index fund, you do not have to do anything. The fund automatically rebalances itself to stay aligned with its index. If the index adds or removes a stock, the fund manager makes that change for you. Dividends paid by the stocks in the fund are automatically reinvested into more shares of the fund (unless you change this setting).

You can check your account anytime to see the current value of your holdings. The value goes up and down with the market. You can also set up automatic monthly or quarterly purchases — many brokerages let you schedule recurring transfers and automatic buys so you do not have to remember to invest each month.

When you are ready to sell, you go to your holdings, click "Sell," enter how many shares you want to sell, and confirm. The sale executes the same way as a buy. Any profit or loss is recorded for tax purposes.

Frequently Asked Questions

Do I have to pay a commission to buy index funds?

No. Nearly all major brokerages charge zero commission on index fund purchases, whether they are mutual funds or ETFs. Some mutual funds charge a small fee called a load (usually 0.5% to 1% of your purchase), but this goes to the fund company, not the brokerage. The fund's expense ratio — the annual fee — is separate and is charged whether you buy or sell.

What is the minimum amount I need to invest?

Most brokerages have no account minimum and let you start with any amount. However, some index mutual funds have minimums of $500 to $3,000 for the first purchase. ETFs have no minimum beyond the price of one share, which ranges from $50 to $400 depending on the fund. Check the fund's details page to see if it has a minimum.

Can I buy index funds inside a retirement account?

Yes. Most brokerages let you open an IRA or other retirement account and buy index funds inside it. The tax treatment is different — gains and dividends are not taxed each year — but the buying process is the same. If your employer offers a 401(k), you can usually direct that money into index funds as well, though the available options may be limited.

What if I want to buy the same fund every month?

Set up automatic investing. Most brokerages let you schedule a recurring transfer from your bank account and an automatic purchase of a specific fund on a set date each month. This is called dollar-cost averaging and removes the need to remember to invest manually.

How long does it take to sell an index fund?

ETFs sell when ready during market hours at the price you see. Mutual funds sell at the market close on the day you place the order. The money from the sale appears in your brokerage account within one to three business days, and you can then transfer it back to your bank.