What Exactly Is an Annuity and How Does It Work?

Let’s start by demystifying the term. An annuity is fundamentally a contract. You make a payment, or a series of payments, to an insurance company. In return, the insurance company promises to make payments back to you, either immediately or at some point in the future. The primary purpose of this arrangement is to create an income stream you can rely on, which is a cornerstone of solid retirement planning.

To understand how annuities work in retirement, it helps to think of them in two distinct phases: the accumulation phase and the payout phase.

First is the accumulation phase. This is the period when you are funding the annuity. You might do this with a single lump-sum payment, perhaps from a 401(k) rollover or the sale of a home. Or, you might make a series of payments over several years. During this time, the money in your contract can grow. How it grows depends on the type of annuity you choose, a topic we will explore in detail shortly. A key feature of this phase is that the growth is typically tax-deferred, meaning you don’t pay taxes on the earnings until you begin to withdraw them.

Second is the payout phase, also known as annuitization. This is the moment you’ve been planning for. You instruct the insurance company to start sending you regular checks. You have many choices here. You could receive payments for a specific number of years, such as 10 or 20. Or, and this is the most powerful feature for many retirees, you could choose to receive payments for the rest of your life, no matter how long you live. Some options even allow for payments to continue to a surviving spouse.

The core idea behind an annuity is to transfer risk. You are transferring the risk of outliving your money (longevity risk) and, in some cases, the risk of poor market performance, to a large, regulated insurance company. They pool the money and life expectancies of thousands of people to make these long-term guarantees possible. In exchange for this security, you are typically giving up some liquidity, meaning you can’t easily access the entire lump sum of your money once the contract is in place, and potentially some of the higher growth you might see in the stock market.

It’s this trade-off—giving up some control and potential upside for a guarantee of lifelong income—that makes an annuity a unique and sometimes valuable part of a retirement plan. It’s not an investment in the same way a stock or a mutual fund is. It’s an insurance product designed to manage a very specific risk: the risk of running out of money.