The Effect of the SEC's XBRL Mandate on Audit Report Lags

There is considerable debate about whether the adoption of eXtensible Business Reporting Language (XBRL) will result in timelier SEC filings. We provide empirical evidence on this debate by investigating the effect of XBRL adoption on audit report lags. Using a hand-collected panel of S&P 1500 clients' XBRL financial report filings and both levels and difference-in-differences analyses, we show that audit report lags decrease following the mandatory adoption of XBRL. These results are robust to various subsamples and model specifications. On average, audit report lags decrease anywhere from 0.4 to 3.4 percent (0.21 to 1.93 days) in the post-adoption period, depending on the specification used. We further document that these results are concentrated among filers with strong internal control systems and no prior XBRL reporting experience. We also find that audit report lags continue to decline in the years following adoption, which is indicative of a learning curve and improvements in XBRL reporting quality. Additional tests reveal that XBRL is negatively associated with audit fees, suggesting that the XBRL effect is at least partially driven by auditor efficiency gains. Our findings are informative for assessing the economic consequences of requiring XBRL adoption, which should be of interest to regulators, managers, and researchers.