Systems and methods for parallelizing customer input with real-time picking for item substitutions

Systems and methods for improving the efficiency of order fulfillment are disclosed. When fulfilling an order in which substitutions are required, due to unavailability of particular products, the process of contacting the customer and receiving a selection from the customer can be separated from the picking process. The picker can continue to fulfill the order, while an automated system offers alternatives and receives selections from the customer. If appropriate, the substitution can be appended to the picker's list. If the picker has completed the remainder of the order, on the other hand, a new order with the substitution can be created, which can later be aggregated with the original order. A variety of methods can be used to efficiently present substitutions to the customer and receive choices from the customer, including use of imagery of substitute items.