The Securities Act of 1934 requires corporate insiders to publicly disclose transactions in their company’s stock within two business days on Form 4. Despite this bright-line legal requirement, we identify more than 100,000 transactions, involving over $122 billion that were disclosed late. The conventional wisdom in the legal community is that these late filings are unintentional clerical errors and that it is a waste of resources to police these “broken windows.” Perhaps as a result of this, the SEC has rarely enforced the filing deadline. We examine the phenomenon of late Form 4 filings and associated lack of enforcement. In contrast to the conventional wisdom, we find that trades reported in late filings are highly opportunistic––they earn significant abnormal returns relative to trades in timely filings and appear intended to conceal trading activity prior to material corporate events. Our evidence suggests that insiders may be exploiting the SEC’s lack of enforcement of filing deadlines, resulting in unusually opportunistic insider trading.