The short answer
A fixed-indexed annuity credits interest based on a market index, but your money is not invested in that index. Built-in limits — caps, participation rates, and spreads — determine how much interest you actually receive. These limits are also why an indexed annuity avoids direct market losses but won't deliver the full index gain.
A fixed-indexed annuity credits interest based on the movement of a market index — but your money is not invested in that index. Instead, the contract uses formulas with built-in limits to turn index movement into the interest you actually receive. Those limits are the caps, participation rates, and spreads. They are the reason an indexed annuity can avoid direct market losses and the reason it won’t hand you the full index gain.
Cap
A cap is a ceiling on the interest credited for a period. If the index rises above the cap, your interest is limited to the cap. If it rises by less than the cap, a cap-only design credits that lower amount. (Many contracts also apply a participation rate or a spread — both covered below — which can further reduce what’s credited, so the cap is rarely the whole story.) The cap is one of the levers an insurer uses to manage what it can guarantee elsewhere.
Participation rate
A participation rate is the share of the index’s movement counted toward your interest. At, say, a participation rate below 100%, only part of the index’s gain is used in the calculation. A product may use a participation rate instead of a cap, or alongside one.
Spread (or margin)
A spread is an amount subtracted from the index’s gain before interest is credited. If the index gains and the spread is taken off the top, you receive the remainder. It’s simply another way the same trade-off shows up.
The trade-off in one sentence
With a fixed-indexed annuity, you give up some potential upside in exchange for not being exposed to the index's losses. Whether that trade fits your goals depends on your timeline, how much you can leave in place, and the contract's guarantees — not just today's rates, which can change at renewal.
You give up some of the upside in exchange for not being exposed to the index’s losses — plus the contract’s other terms, like surrender periods. Whether that trade is worth it depends on your goals, your timeline, and the money you can leave in place. And because these features can change at renewal, the honest evaluation looks at the guarantees, not just today’s numbers.
Common questions
What is a cap in a fixed-indexed annuity?
A cap is the maximum interest rate the annuity will credit for a period, even if the index it tracks rises more. If the index gains more than the cap, your credited interest is limited to the cap. Caps are one of the features that keep an indexed annuity an insurance product, not a market investment.
What is a participation rate?
A participation rate is the percentage of the index's movement that is used to calculate your interest. At a participation rate below 100%, you receive only part of the index's gain for that period. Some products use a cap, some a participation rate, some a spread — and some a combination.
Is my money invested in the stock market?
No. In a fixed-indexed annuity your money is not invested directly in the index or the market. The index is only used as a reference to calculate interest, within limits like caps and participation rates. Your credited value is not exposed to market losses, but you also do not receive the full index gain.
Can these rates change?
Often yes. Caps, participation rates, and spreads can be set for a period and adjusted by the insurer at renewal, within the contract's guarantees. Understanding how and when they can change is an important part of evaluating any indexed annuity.
Related: What a fixed annuity guarantees · Annuities, explained