This study investigates the determinants and effects of voluntary book-tax difference (BTD) disclosures in earnings releases. Unlike prior studies, I find no evidence that managers are more likely to voluntarily disclose BTD information when firms have low earnings quality. I also find that managers are more likely to disclose BTD information when firms have large negative but not large positive BTDs. Because BTDs are particularly informative when earnings quality is low and when book income significantly exceeds taxable income (i.e., large positive BTDs), these results suggest that managers selectively disclose BTD information in earnings releases. Interestingly, I also find that managers are more willing to disclose BTD information when tax avoidance activities are high. This result suggests that managers are willing to bear some taxrelated disclosure costs to reassure investors that BTDs are not due to aggressive financial reporting. Prior research provides evidence of a systematic association between BTDs computed using required 10-K tax disclosures and future forecast errors and stock returns. I provide evidence that voluntary BTD disclosures attenuate the association between BTDs and future forecast errors. I also provide limited evidence that voluntary BTD disclosures attenuate the association between BTDs and future stock returns. These results suggest that voluntary BTD disclosures help analysts and investors impound BTD information into earnings forecasts and stock prices. / text