The Accumulation Period is the time during which an investment product with a future structured payout is open to a build up assets for future distribution.
An example would be a fixed annuity that is purchased when an investor is age 40, and is set it begin lifetime monthly payouts at age 65. While the fixed annuity is initially funded with an opening deposit, it can offer the investor the option of making additional deposits at any time during the time from when the annuity was purchased until it begins making its first of many periodic payouts at age 65. Many times investors make an initial opening deposit and make periodic investments into the annuity at set intervals in an effort to maximize the balance in the annuity. The time the annuity is available for additional deposits before its first payout is referred to as the Accumulation Period.