We investigate why book-tax temporary differences appear to serve as a useful signal of earnings persistence. We maintain that there are multiple potential sources of large positive book-tax differences and examine the differing implications of large positive book-tax differences for earnings and accruals persistence depending on the source of those differences. We expect and observe that firms with large positive book-tax differences likely arising from tax avoidance exhibit greater accruals persistence than other firms with large positive book-tax differences. We also expect and observe that firms with large positive book-tax differences likely arising from upward earnings management exhibit lower earnings and accruals persistence than other firms with large positive book-tax differences. Further, we provide evidence that investors are able to look through to the source of large positive book-tax differences allowing them to correctly price the persistence of accruals. Together, our results illustrate the importance of considering the source of book-tax differences when using them as a signal of earnings quality.