What to know about savings bonds – securities you can buy from the US Treasury

• A savings bond is a debt instrument that's distributed and backed by the US government.
• The federal government issues two types of savings bonds: Series EE and I bonds.
• Series EE bonds double in value if held for at least 20 years, while I bonds keep pace with inflation.
• Visit Insider's Investing Reference library for more stories.

A savings bond is a debt security you can buy from the US Treasury. Both types of savings bonds – Series EE and Series I – are "zero coupon," which means they pay interest only when they're redeemed.

Savings bonds tend to offer low returns, but "they are extremely low-risk as they are backed by the US government," says Michael James Kelly, Certified Financial Planner, CFA, and owner of Switchback Financial.

This type of investment could be a good fit for a long-term portfolio in some cases, but you should know about what they earn, how they're taxed, and how to buy them.

Series EE vs. Series I

When you buy a savings bond, you're essentially lending money to the US government, which promises to repay you within 30 years. The main difference between the two types of savings bonds is how the interest works:

• Series I bonds are designed to protect your money from losing value due to inflation. The annual interest rate is made up of two parts: a fixed rate and an inflation-adjusted rate that's calculated twice a year. If deflation occurs, the interest rate won't drop below zero.
• Series EE bonds are guaranteed to double in value if you hold them for at least 20 years. These earn a fixed interest rate, though Series EE bonds purchased before May 2005 have either a variable or fixed rate, depending on the issue date.

"EE bonds, at least right now, are best suited for long-term investors," says Jeremy Keil, a Certified Financial Planner, CFA, and owner of Keil Financial Partners. "If you are shorter-term and think you'll cash out in the next one to five years, you'll probably do better with I bonds. I bonds are also guaranteed to keep up with inflation, and very few investments are guaranteed to do that."

Series bonds rates and taxation

Once you purchase a savings bond, interest is credited every month and compounded twice a year. Rates on new bonds change every April and November, and series I bonds also have semiannual rate changes. You can find these rates and their changes directly from the TreasuryDirect website.

Savings bond investors pay federal taxes on interest earned, but not state or local income tax, says Mark Steber, the chief tax information officer at Jackson Hewitt Tax Services. You have a choice on when to pay those taxes, though.

"Taxpayers can choose to pay taxes on the interest increase for each year when filing that tax return," Steber says, "or they can pay taxes when the bonds are cashed in or reach final maturation date."

The decision typically comes down to the individual and their own tax situation. But generally, "I think that waiting is the best option," Kelly says. "You can benefit from investing that money that could be used to pay taxes annually and gain from the time value of money." However, if you expect your federal taxes to be higher at a later date, then it may make sense to pay taxes as interest is earned.

Whether you have to pay taxes also depends on who bought the bond, who owns it, and sometimes where you live. Check out this table to see which situation applies to you:

Pros and cons of savings bonds

Like any financial investment, savings bonds come with some benefits and drawbacks. Consider these points before taking out a savings bond:

How to buy savings bonds

All savings bonds used to be issued on paper slips, but now savers have two options:

• Buy online. You can purchase bonds electronically at TreasuryDirect.gov, the US Treasury's electronic savings portfolio platform. Once you open an account, you'll choose the type of bond you'd like to buy and the denomination. Both are available in penny increments between $25 and $10,000. Your online account is where you can go to track your bonds' growth, make purchases, and reinvest.
• Buy paper: You can purchase an additional $5,000 in paper I bonds using your IRS tax refund when you file your annual income tax return.

Once you have the bond, you decide how long you'll hold onto it, anywhere between one and 30 years. EE bonds double in value after 20 years - but you'll need to wait the full term to get the maximum return on either type of bond. Cash in before that point, and your return will be based on a maturation schedule that rises over the course of the bond's term.

The financial takeaway

Savings bonds provide a safe haven for your money since they're backed by the US government. While Series EE bonds double in value if you hold them for at least 20 years, Series I bonds could be more beneficial if inflation continues to rise while savings rates stay low.

"Instead of keeping mid-term cash in a savings account or CD," Kelly says, "one could hold the money in a Series I bond and hedge against inflation while getting a higher rate."

Either way, both types of bonds are typically seen as a long-term investment - so consider including these in your portfolio if you have time to let them fully mature.

What is hyperinflation? Understanding the rapid increase in the cost of goods and services over timeBonds can be taxable or tax-free - here's your guide to the different types and calculating what's due on themBonds vs. CDs: The key differences and how to decide which income-producing option is better for youBonds can be taxable or tax-free - here's your guide to the different types and calculating what's due on them