A cash balance plan is a type of defined benefit plan that resembles a defined contribution plan. For this reason, these plans are referred to as hybrid plans. A traditional defined benefit plan promises a fixed monthly benefit at retirement that is usually based upon a formula that takes into account the employee's compensation and years of service. A cash balance plan looks like a defined contribution plan because the employee's benefit is expressed as a hypothetical account balance instead of a monthly benefit.

Each employee's "account" receives an annual contribution credit, which is usually a percentage of compensation, and an interest credit based on a guaranteed fixed rate or some recognized index like the 30 year U.S. Treasury bond rate which could vary. This interest credit rate must be specified in the plan document. At retirement, the employee's benefit is equal to the hypothetical account balance which represents the sum of all contributions and interest credits. Although the plan is required to offer the employee the option of using the account balance to purchase an annuity benefit, most employees will take the cash balance and roll it over into an individual retirement account (unlike in many traditional defined benefit plans which do not offer lump sum payments at retirement).

As in a traditional defined benefit plan, the employer bears the investment risks and rewards in a cash balance plan. An actuary determines the contribution to be made to the plan, which is the sum of the contribution credits for all employees plus the amortization of the difference between the guaranteed interest credits and the actual investment earnings (or losses).

Employees appreciate this design because they can see their "accounts" grow, but they are still protected against fluctuations in the market. In addition, a cash balance plan is more portable than a traditional defined benefit plan since most plans permit employees to take their cash balance and roll it into an individual retirement account when they terminate employment or retire.