On April 9, 2018 Vistra Corp closed its acquisition of Dynegy following a FERC determination that the $1.7 billion deal raised no competitive concerns.

[9] NGC was purchased by Noble Affiliates, Inc. and Apache Corporation, independent oil and gas exploration and production companies, for a reported $50 million in 1989.

[11] In 1993, LG&E Energy Corporation took a stake in NGC, which by then was the largest independent natural gas marketing firm in the United States and had revenues of more than US$2 billion.

The company also admitted on April 26 that it made a large accounting error on a fuel contract, which further depressed the stock price 22 percent.

[36] Desperate for cash, Dynegy sold the Northern Natural Gas Company to MidAmerican Energy Holdings for $928 million on July 29 ($572 less than it paid for it).

[46] On September 24, Dynegy announced that it had agreed to pay a US$3 million fine for using the Catlin company and other business partnerships to hide losses and taxable income.

[49] Still needing cash, Dynegy sold its Hornsea natural gas storage site in the United Kingdom to help pay the fine.

In June 2003, Jamie Olis (former Senior Director of Tax Planning), Gene Foster (former Vice President for Taxation), and Helen Sharkey (a former employee in Dynegy's risk control and deal structure groups), were indicted on numerous counts of mail and wire fraud.

ABG secured loans from Citigroup, Credit Suisse First Boston, and Deutsche Bank to buy natural gas at market prices.

[57] Former chief financial officer Robert Doty agreed to pay a $376,650 fine in October 2007 for his role in helping to conceal the ABG Gas Supply scheme.

[71] In March 2005, it agreed to settle a 1999 dispute with the Environmental Protection Agency by spending US$321 million to repair and upgrade coal-fired generating plants in Illinois to reduce pollutants.

In August 2009, LS Power agreed to buy nine electrical generating plants from Dynegy for US$1.025 billion in cash in order to dissolve the joint venture.

Dynegy's shares fell 80 percent in the two years after the deal closed, and the company posted a large $345 million loss in the second quarter of 2009.

In September 2007, New York Attorney General Andrew Cuomo sued Dynegy and other utilities, arguing that the companies were not properly accounting for the financial risks that pollutants from coal-fired generating plants created.

[78] After a year of negotiations and legal maneuvering, Dynegy agreed to issue statements to its current and future investors warning that government regulation of carbon emissions and lawsuits over pollution could pose financial risks to the company.

Legal counsel advised that Delaware law (under which Dynegy was incorporated) considered a postponement a new meeting, and that would require notifying shareholders (again) and giving at least 20 days' notice.

Legal counsel also believed that Dynegy management would be forced refile resolution with shareholders and resolicit votes, which would delay a meeting until early 2011.

This legal maneuver took advantage of a Delaware Supreme Court ruling which made it difficult for creditors to sue an LLC's board of directors for failing to uphold their fiduciary duty.

[102] On March 8, 2011, Dynegy submitted financial filings with government regulators warning investors that it faced bankruptcy if it could not restructure its debt.

On November 8, 2012, members of International Brotherhood of Electrical Workers (IBEW) Local 320 struck the Roseton and Danskammer plants after a contract extension expired and Dynegy continued to seek cuts in retirement benefits.

Under the terms of the auction, ICS NY had to replace or find a substitute for its credit support agreement, and pay its portion of the plant's outstanding property taxes.

[124][125] As the deal worked its way through state and federal regulatory approval, Dynegy took advantage of low interest rates and refinanced its debt.

The Federal Energy Regulatory Commission (FERC) had to approve the deal and ensure that there was no negative impact on consumers from Dynegy's expanding market share in the Midwest.

[132][133][134] ACM Partners, a financial firm hired by the Sierra Club, also argued that Dynegy purposefully left IPH significantly underfunded and unable to tap into the parent company's resources.

[125] Dynegy disagreed, but the firm warned that if IPH went bankrupt, workers would lose pensions and local communities would have to pay for any environmental remediation.

Julien Dumoulin-Smith, executive director of UBS Investment Research, said Dynegy is far more likely to shutter all five coal-powered plants rather than add pollution control devices.

Dumoulin-Smith said that the United States Environmental Protection Agency (EPA) issued final rules on sulfur dioxide emissions that go into effect in July 2018.

The remaining four plants are borderline cases with the exception of Duck Creek Station which spent nearly US$800m on sulfur dioxide removal, and may also be forced to close if EPA regulations tighten in the future (a highly likely possibility, he said).

[139] On April 9, 2018, Vistra Corp closed its acquisition of Dynegy following a FERC determination that the $1.7 billion deal raised no competitive concerns.

[7] In June 2021, the Attorney General of Illinois filed a lawsuit against Dynegy claiming that the company polluted groundwater with contaminants from coal ash.