Federal Court Reinstates 5% Safe Harbor for Solar and Wind Tax Credits

WASHINGTON — A federal court has handed the renewable energy industry a significant victory, reinstating a key provision for claiming federal tax credits just weeks before a critical deadline. In a ruling issued on June 6, 2026, the U.S. District Court for the District of Columbia vacated an Internal Revenue Service notice that had eliminated the “5% safe harbor” for wind and solar projects, a crucial pathway for developers to establish their eligibility for valuable clean energy incentives.

The decision in the case, Oregon Environmental Council v. Internal Revenue Service, overturns guidance issued by the Trump administration in August 2025. That guidance, known as IRS Notice 2025-42, had specifically targeted wind and large solar projects, removing a long-standing method for proving that construction had officially begun on a project. This restoration provides developers with renewed certainty as they race to meet a July 4, 2026, deadline to qualify for Section 45Y and 48E tax credits.

At the heart of the issue is the concept of “beginning of construction,” or BOC. To qualify for the full value of certain federal tax credits, developers must demonstrate that work started by a specific date. The IRS had long provided two primary methods for doing so. The first is the “Physical Work Test,” which requires showing that physical work of a significant nature has commenced. The second, and often more practical for large-scale projects with long lead times, was the 5% safe harbor.

First established by the IRS in 2013, the safe harbor allowed developers to meet the BOC requirement by incurring at least 5% of the total project costs before the deadline. This financial-based test provided a clear, predictable, and verifiable standard that was vital for securing financing and planning complex, multi-year energy projects. The Trump administration’s move to eliminate this option for wind and solar was a direct result of a July 2025 executive order aimed at ending what it termed “market distorting subsidies” for renewable energy sources.

By issuing Notice 2025-42, the IRS forced developers of new wind and solar facilities to rely exclusively on the more demanding and often ambiguous Physical Work Test. A consortium of environmental and governmental organizations, including the Natural Resources Defense Council, challenged the notice, arguing it would cause direct harm by increasing electricity prices, adding to air pollution from fossil fuel plants, and derailing clean energy projects that would have otherwise qualified for the credits.

In her ruling, Judge Colleen Kollar-Kotelly determined that the IRS notice was “arbitrary and capricious.” The court’s opinion stated that the agency failed to provide a reasoned explanation for its abrupt change in policy, particularly its decision to single out wind and solar while leaving the safe harbor intact for other technologies. The judge wrote, “The natural economic consequence of the Notice is less clean electricity generation capacity and higher electricity prices.”

The decision was celebrated by clean energy advocates. David Villagrana, Lead Counsel for the Environmental Defense Fund, which filed a brief in the case, said, “Vital solar and wind power projects will be able to move ahead now that the court has ruled.” Bill Curtis, an attorney at Spencer Fane, described the ruling as a “significant victory for the industry as it provides an extra layer of certainty for those who want to claim the credit.”

This ruling arrives at a critical moment. Under current law, the relevant tax credits begin to phase down for projects that are not placed in service by the end of 2027. However, an exception exists for projects that began construction on or before July 4, 2026. The restoration of the 5% safe harbor gives developers a viable path to meet this fast-approaching deadline, potentially unlocking billions of dollars in investment.

Despite the victory, some legal experts advise caution. The court remanded the matter to the IRS for “further administrative action,” which leaves the door open for the agency to issue revised guidance. In a blog post, the law firm Foley noted that the potential for an appeal of the ruling and the short timeline before the July 4 deadline make it potentially risky for developers to rely solely on the restored safe harbor.

While this ruling provides welcome clarity for developers, the underlying volatility highlights a persistent challenge for businesses operating in sectors heavily influenced by tax policy. The sudden removal and subsequent judicial reinstatement of a critical financial planning tool underscore how quickly the regulatory ground can shift. In our experience, navigating these complex and shifting tax landscapes is a major hurdle for mid-sized companies whose financial models depend on regulatory stability. This kind of uncertainty can stall projects and deter investors, making proactive and flexible financial strategy essential. This is precisely where our firm's expertise in tax preparation and compliance becomes critical. We help clients structure their projects and finances to remain compliant while maximizing available incentives, regardless of last-minute court decisions. Business owners facing such uncertainty can learn more about building a resilient tax strategy with C&S Finance Group LLC at csfinancegroup.com.

Moving forward, all eyes will be on the IRS to see how it responds to the court's decision. The agency could choose to appeal the ruling, accept it, or attempt to issue new guidance that addresses the court's objections. In the interim, solar and wind developers will be working quickly to document their project expenditures to take advantage of the restored safe harbor before the July 4 deadline passes.