(WASHINGTON, D.C.) – A federal court in Washington, D.C. struck down IRS Notice 2025-42, reinstating the prior 5% or physical-work pathways for beginning construction on wind and solar projects and putting fresh attention on fast-approaching deadlines as developers race to qualify for clean-energy tax credits.

Judge Colleen Kollar-Kotelly vacated the notice in Oregon Environmental Council v. Internal Revenue Service, Case No. 1:25-cv-04400. The ruling resets the begin construction rules to the framework developers had used for years before the Internal Revenue Service changed course. In practice, that means projects again may qualify by meeting the 5% safe harbor or by starting physical work of a significant nature.

IRS Notice 2025-42 had narrowed those options. It tightened begin construction standards for wind projects and for solar projects larger than 1.5 megawatts, while leaving the 5% test in place for smaller solar facilities. That split treatment became a central problem in court. The notice singled out wind and larger solar projects without applying the same limits across other energy facilities.

In the district court’s view, the agency did not supply an adequate reasoned basis for that distinction. Judge Kollar-Kotelly found that the Internal Revenue Service unlawfully changed standards for solar and wind facilities without justifying the disparate treatment. That matters beyond one notice. Federal agencies generally need a clear explanation when they depart from an established rule and impose a different standard on one set of regulated parties.

Developers had challenged the notice because begin construction status often anchors the economics of a project. Tax credits affect pricing, investor interest, construction schedules, equipment orders, and debt terms. A narrower test can shift all of those pieces at once. Tax equity investors, in particular, often look closely at whether a project has a defensible path to credit eligibility before committing capital.

Congress had set a transition period for wind and solar projects to qualify for the relevant credits if they began construction before the statutory deadline. The notice changed how some projects could satisfy that requirement. After the vacatur, the older framework is back in place unless a higher court or new agency action changes it again.

The restored pathways are straightforward in concept, even if project facts still require careful review. One route allows a developer to show begin construction by incurring at least 5% of total project costs. The other allows the project to qualify by starting physical work of a significant nature. Those two tests have long shaped planning for wind and solar deals, and they usually affect procurement strategy as much as field construction.

That distinction is often practical rather than abstract. Some projects rely on early equipment spending to satisfy the 5% safe harbor. Others are structured around site work, foundations, or other construction activity that may support the physical-work test. The choice can affect when a project closes financing, how developers document costs, and what tax counsel asks investors to verify before funds are released.

The timing pressure is sharper because the date now hanging over the market is July 4, 2026. Projects that do not establish begin construction by then may lose access to the transition treatment tied to these tax credits. The vacated notice had made that deadline harder to meet for many wind and larger solar projects by removing one of the two main paths they had expected to use.

Financing consequences may arrive quickly. Tax equity structures are built on assumptions about credit availability, and those assumptions feed directly into valuation and closing conditions. A project that can credibly point to the restored 5% test may look different to investors than the same project did under IRS Notice 2025-42. Lenders and sponsors may also revisit delayed transactions, especially where the notice had forced a rewrite of milestone schedules or procurement plans.

Solar developers sit in a slightly different position depending on project size. The notice had preserved the 5% route for smaller solar facilities while restricting larger ones, using the 1.5 megawatts threshold as the dividing line. By vacating the notice, the court removed that distinction. That may reduce one source of uneven treatment inside the solar market, where project sponsors had been working under different begin construction expectations based largely on size.

The legal posture still deserves close attention. A federal district court ruling typically binds the parties before it, but a vacatur of agency action can have broader practical effect because the challenged notice is set aside rather than merely ignored for one plaintiff. Even so, developers and investors will want to watch whether the government seeks a stay, files an appeal, or issues interim guidance. Any of those steps may affect how cautious market participants choose to be in the near term.

Further agency action also remains possible. The Internal Revenue Service and Treasury may try to replace the notice with a new rule supported by a fuller explanation, or they may decide that the statutory deadline is too close for another narrow rewrite. If regulators act again, they will likely face the same basic problem identified by Judge Colleen Kollar-Kotelly: a departure from established begin construction standards needs a reasoned explanation, especially where wind and solar projects are treated differently from other credit-eligible facilities.

Project sponsors do not need to wait for that next step to assess exposure. They may want to confirm cost-incurrence records, construction documentation, board approvals, procurement dates, and tax opinions now, while the pre-notice framework is back in effect. Deals tied to the July 4, 2026 deadline will likely be reviewed line by line. The same is true for tax equity commitments that were priced under the assumption that IRS Notice 2025-42 would survive.

This article discusses tax policy and court decisions that may affect tax credits for renewable-energy projects. Consultation with a tax professional is advised for individual project planning.

Legal considerations are presented for informational purposes and do not constitute legal advice.