What: Shares of measurement company comScore (SCOR -0.73%) tumbled on Tuesday after the company missed a self-imposed deadline to provide an update on its ongoing audit of certain accounting issues. At noon, the stock was down about 20%.

Image Source: comScore.

So what: On Feb. 19, comScore's board of directors received a message regarding potential accounting issues. The company delayed filing its annual report and quarterly report for the first quarter, giving the Audit Committee time to conduct a review of the problems. On May 11, comScore filed a form with the SEC stating that the investigation was nearly complete, and that it planned to provide an informed update by June 27.

The company's June 27 update was not what investors were hoping for. A filing with the SEC stated that the Audit Committee requires more time to evaluate the collected information and draw final conclusions. The company failed to provide a new deadline, instead saying that it plans to file its annual and quarterly reports as soon as is reasonably practicable.

Now what: Accounting issues, particularly the kind that delay the filing of reports, are never good news. The company's inability to wrap up its review by its own deadline suggests that the problems could be deeper than previously assumed. It remains unclear how much longer the review process will drag on, and investors are punishing the stock as a result.