U.S. government bills or notes
Treasuries are backed by the full faith and credit of the U.S. government. Treasury bills typically mature in less than a year, while Treasury notes often take between two and 10 years to mature. They're considered extremely safe, and you can buy them commission-free online. They're also exempt from state and local taxes.
But you may be able to earn a higher return with some of the other options listed here. Also, like most bonds, if you need to withdraw your funds before the maturity date, you may not get your full investment back.
I bonds
I bonds are a special type of bond that's designed to protect your investment against inflation. You can purchase them in increments ranging from $50 to $10,000 and buy them directly online without paying a commission fee.
An I bond is also exempt from state and local taxes and might be tax-free if you use the money for post-secondary education expenses. If you do owe taxes on your earnings, you may defer them for up to 30 years. But you must make sure to hold your I bond for at least five years. Selling it earlier results in a penalty.
Municipal bonds
Municipal bonds are issued by state and local governments. Like all bonds, they're essentially debt. The governments take this money to use on public works and pay you back with interest. While they're not as safe as U.S. government bonds, municipal bonds are still considered low risk, and they're exempt from federal taxes (and possibly state and local taxes).
Unlike U.S. government securities, municipal bonds may charge a commission fee. You also may not earn as much with these as you could with some of the other options on this list, especially if you sell your bond before its maturity date.
Corporate bonds
Corporate bonds are debts issued by companies. Bonds from more creditworthy companies are generally considered safer, but you may earn smaller returns. Meanwhile, bonds from less creditworthy companies could earn you bigger returns, though there's a greater risk of loss.
You'll likely have to pay a commission to purchase a corporate bond, and selling yours early could cost you money.
Bond funds
Bond funds are mutual funds that pool the money of many investors to purchase a variety of bonds. They help you quickly diversify your investments, which can better protect you against loss. But they're a little less predictable than some of the other investments listed here because the share price and yield can fluctuate.
Mutual funds also charge an annual fee known as an expense ratio, which eats up some of your profits. You may pay a commission fee, known as a load, as well.
You don't have to choose just one
You're free to spread your cash out over several accounts detailed above. Remember, what's right for you now may not be right for you later on, so periodically review where to park your cash. Compare the fees and returns at different types of bank accounts or investments, as these can change over time.