A regular forward contract in which the notional is determined over the lifespan of the option rather than as a preset amount. This structured product provides institutional investors and corporates with a forward hedge, especially in cases where the spot price of an underlying is expected to move in either direction or in a specific range. When the spot condition (price movement direction or price range) is satisfied, the accumulator gets initiated. The number of fixings on which the spot condition is satisfied within time to maturity determines the proportion of the notional that should be paid.

The main types of such an option include accumulator in option and accumulator out option.