ComScore, the troubled measurement company that has spent the past year trying to untangle an accounting mess linked to its former CEO, watched its stock plunge more than 20% Monday after it said it would miss a required NASDAQ filing deadline and could have its stock delisted from the exchange.

ComScore stock, whic had traded as low as $23.05 each on Monday (down 29%), finished the day at $23.22, down 28.4% ($9.22 each).

In a statement, ComScore said it has notified the Nasdaq Hearings Panel (the "Panel") that it will be unable to regain compliance with its Securities and Exchange Act periodic reporting requirements by the February 23, 2017 deadline set by the Panel.

In October, the Panel said it would provide ComScore with a conditional listing on the NASDAQ Global Select Market through Feb. 23, the give the company extra time to complete its financial restatement and regain full compliance.

While ComScore said it has made “significant progress” in the restatement process, it won’t make the deadline. The delay relates to “the magnitude of work” associated with reviewing accounting judgements and estimate for transactions over a period of three years. ComScore now says it will be able to complete the restatement and become current in the filing of all the required reports this summer, but said there can be no guarantees that the process will be completed at that time.

ComScore first revealed accounting irregularities last year when it notified the SEC that its board had received a message regarding “certain potential accounting matters,” and began an investigation. Later the company said it had found some potential problems in the way it reported non-monetary revenue – essentially barter transactions – that could have helped artificially boost the compensation for then CEO Serge Matta and other executives. Matta resigned later that year and was replaced with board member and co-founder Gian Fulgoni.

"Although we are disappointed that we will not meet NASDAQ's deadline, we have made significant progress towards the restatement and in strengthening our internal audit and compliance functions,” Fulgoni said in a statement. “Furthermore, our business fundamentals continue to be strong, underscored by our healthy balance sheet with $116 million in cash. We are confident in our strategy, our roadmap for innovation, our unique data and technology assets, and in the value we deliver to more than 3,000 clients, all of which we believe will drive long-term growth for our company."

ComScore said that in the event its stock is delisted from the NASDAQ, it will file an appeal requesting that any action be delayed and consider providing the company more time to complete the process while remaining listed. If that isn’t possible, ComScore said its shares would be listed over the counter until it could regain compliance and its NASDAQ listing.

ComScore stock rose 7% ($2.12) each to $32.20 per share in afternoon trading Friday after the measurement company said it will restate its revenue for the past three years after a months-long accounting review.

ComScore first revealed the review back in March, adding that it had been made aware of certain accounting practices in the month prior that warranted a closer look. In August comScore founder and executive vice chairman Serge Matta gave up the CEO role to company co-founder Gian Fulgoni.  On Sept. 12, Matta said he will resign from the company entirely as of Oct. 10.

In a conference call with analysts Friday morning, Fulgoni said he is “very much committed to ensuring that we get the company back on the right track and I think we can do that.”

ComScore shares fell hard ever since it revealed potential accounting issues in March – its stock fell 30% a that time and another 30% in June when it said the investigation would take longer than expected. But the shares have managed to regain some of that ground over the past few months.

In a filing with the Securities and Exchange Commission comScore said 2015 revenue will be restated to $339.9 million (about 8% lower than originally reported) and its loss from operations for that year is now $10.8 million, about four times larger than previously stated. In addition, comScore restated revenue for 2013 -- $312.9 million instead of $329.2 million; and for 2014 -- $283.6 million instead of $286.9 million. The discrepancies mainly involved non-monetary transactions.

ComScore had been in the habit of reporting barter transactions – like exchanging data with other companies – as revenue, which was pointed out in a Wall Street Journal article last year.

In the filing comScore said as a result of the investigation to date, “cannot support the prior accounting for the nonmonetary transactions.” The company said as the investigation concludes, it “also will be undertaking a significant effort to help ensure that the errors in judgment and internal control deficiencies did not impact other transactions that were not part of the investigation. Therefore, there may be additional accounting adjustments as a result of these efforts and such adjustments may be material.”

In a note to clients Friday, Telsey Advisory Group media analyst Tom Eagan said the SEC filing could mean “we could be closer to scraping the bottom of the barrel of bad news,” but added other questions regarding whether the company’s 2013-2015 statements will have to be re-audited or if Rentrak shareholders will sue. ComScore completed its purchase of Rentrak in an all-stock deal worth about $779 million in January.

ComScore stock plunged more than 30% ($7.66 each) to $21.74 per share in early trading Tuesday after the measurement company said it would require more time to file its 10-K annual and 10-Q quarterly reports with the Securities and Exchange Commission.

The stock closed at $23.81 per share June 28, down 19% or $5.59 each.

ComScore revealed in March that its board of directors received a message regarding potential accounting matters at the company. While details regarding those potential matters weren’t revealed, its Audit Committee immediately began a review of the matters with independent counsel and advisors. ComScore had said in May that it expected to provide a further update on its progress by June 27.

The announcement came about one month after comScore completed its merger with set-top box measurement pioneer Rentrak, creating a more formidable rival to powerhouse Nielsen. 

In its update, filed with the SEC on June 28, comScore said that its Audit Committee “continues to work vigorously to complete its review and to report its findings to the Board,” adding that the committee has completed a substantial amount of the factual inquiries in the review.

But the committee added that it would need more time “to evaluate the information collected and to reach and evaluate final conclusions.”

In a research note, Telsey Advisory Group media analyst Tom Eagan wrote that while investors weren’t expecting that the 10-K and 10-Q would be filed, they did hope for a little more detail from the company.

“Our take on the 8-K is that the company is farther away from resolving its accounting issues than we had expected,” Eagan wrote.” Our concern is that any revisions to its financial statements do not reflect just reductions in Non-Monetary Revenue (NMR), but lower Stock-based Comp (SBC) and dis-synergies with the integration of Rentrak's operations.”

Eagan downgraded the stock to "market perform" from "outperform," lowering his 12-month price target to $30 per share from $60.