In this study, we examine whether not-for-profit organizations actively manage their pension accounting assumptions and whether their assumptions are, as prior research suggests, more aggressive than those of for-profit organizations. Using a 17-year panel dataset collected from audited financial statements, we compare the accounting assumptions (the expected rate of return and the discount rate) of not-for-profit and for-profit firms. We also examine the not-for-profit sample alone to test for accounting bias motivated by various financial incentives. We model accounting assumptions as levels (between-firms) as well as changes over time (within-firms). Contrary to prior research, we find no evidence that not-for-profits use more aggressive assumptions than for-profits. Furthermore, we find that most of the accounting biases of not-for-profits are explained by between-firm variation rather than within-firm variation, suggesting that although not-for-profits use biased assumptions, they may not actively adjust them to target financial benchmarks.