These studies examined how the practice of accounting for one's time-so that work can be billed or charged to specific clients or projects-affects the decision to allocate time to volunteer activities. Using longitudinal data collected from law students transitioning to their first jobs, Study 1 showed that exposure to billing time diminished individuals' willingness to volunteer, even after controlling for attitudes about volunteering held before entering the workforce as well as the individual's specific opportunity costs of volunteering time. Studies 2-5 experimentally manipulated billing time and confirmed its causal effect on individuals' willingness to volunteer and actual volunteering behavior. Study 5 showed that the effect of exposure to billing time on volunteering occurred above and beyond any effects on general self-efficacy or self-determination. Individual differences moderated the effects of billing, such that people who did not value money as much were less affected.