I investigate whether there is a tradeoff between required timeliness and detail of firms' mandatory disclosure of material events and whether such a tradeoff has capital market consequences. Specifically, I examine an SEC regulatory change that accelerates the deadline for reporting material events via Form 8-K. I find that after the regulatory change, there is a general decline in the length of and quantitative information included in 8-K disclosures and that 8-Ks more constrained by the increase in required timeliness experience a greater decrease in disclosure detail than less constrained 8-Ks. Firms filing 8-Ks that are more constrained by the regulatory change also exhibit a greater increase in information asymmetry and investor disagreement around the 8-K filing date. Moreover, I find evidence consistent with the required timeliness-detail tradeoff driving the incremental increase in investor disagreement for firms filing constrained 8-Ks. These findings should be of importance to regulators concerned with both the timeliness and quality of mandatory disclosure and to managers and investors interested in the costs of required disclosure timeliness.