Recent evidence suggests that offloading demands on to external sources can improve the remembering of future plans (i.e., prospective memory). The purpose of the current study was to better understand the mechanisms by which participants choose to offload prospective memory demands. Participants formed the intention to later respond to either one (low load) or four (high load) prospective memory targets with or without the use of reminders. During reminder trials, participants could press the "reminder" key to be shown the learned targets in a "lookup table." The frequency of reminder checking was used to index the willingness to rely on external sources to support remembering. The utility of reminder checking was manipulated by varying the number of distractors presented in the lookup table (Experiment 1), implementing a time penalty for checking the table (Experiment 2), and explicitly describing the effectiveness of using reminders (Experiment 3). The results consistently showed that participants checked reminders more frequently under high memory load (i.e., four targets). Moreover, participants checked reminders less frequently when the costs associated with doing so increased (Experiments 2 and 3). However, confidence in one's own memory ability was not associated with checking frequency. These findings suggest that participants choose to offload, at least in part, to reduce the time or effort to complete the task.