The doctrine, briefly
The economic substance doctrine isn't new. Courts have applied some version of it for decades, disallowing tax benefits from transactions that lacked real economic motivation beyond the tax outcome itself. Congress codified the doctrine in 2010 under Section 7701(o), turning what had been a judicial patchwork into a defined statutory test with real teeth: a 20% penalty if the position is disclosed on the return, and 40% if it isn't.
The test itself has three parts. Economic substance analysis has to be relevant to the transaction in the first place. The transaction must produce a meaningful change in the taxpayer's non-tax economic position. And the taxpayer needs a substantial non-tax purpose, generally measured by whether the pre-tax profit, on a present-value basis, exceeds fees and transaction costs.
There's a reason the tax credit industry hasn't spent fifteen years worrying about this. The legislative history behind Section 7701(o) includes a footnote stating that tax credits Congress designed to encourage a specific type of investment — the production tax credit, the low-income housing credit, the energy credit among them — generally shouldn't be disallowed under economic substance analysis when a taxpayer, in form and substance, actually does the thing the credit was meant to encourage. Build a wind farm to get the PTC, and you're doing exactly what Congress had in mind.
What's changed
That footnote protects the core transaction. It doesn't protect everything wrapped around it. A deal with unusual fee structures, layered financing, or arrangements that seem designed mainly to move value between parties rather than build and operate a project can still draw scrutiny, even if the underlying facility is squarely within the credit's purpose.
Recent Tax Court activity has kept this doctrine active and, in places, expanded its reach. In April 2026, the Tenth Circuit affirmed in Liberty Global v. United States that technical, mechanical compliance with the tax code doesn't automatically shield a transaction that lacks real economic substance — a ruling outside the energy credit space, but one that reinforces how far courts are willing to look past formal structuring. In February 2026, the Tax Court in Otay Project LP v. Commissioner disallowed a $714 million deduction from a related-party transaction it described as "engineered," finding no meaningful economic effect beyond the tax benefit. And in a captive insurance case decided in November 2025, the Tax Court confirmed that the codified doctrine can deny benefits from specific pieces of a transaction without disregarding the whole arrangement — meaning a project's core credit could survive while a surrounding structure gets unwound.
None of these cases involves clean energy tax credits directly. That's part of why insurers are paying closer attention now rather than later: the doctrine is being tested and sharpened in adjacent areas first, and underwriters would rather understand its edges before a clean energy case becomes the test.
What this means for underwriting
Tax credit insurers are increasingly asking deal teams to walk through the commercial rationale for a transaction's structure, not just its compliance with the specific credit section being claimed. That's a different question than the FEOC and material assistance diligence that has occupied most underwriting bandwidth recently, which we covered in the insurance policy quietly holding the FEOC market together. FEOC risk is binary and eligibility-driven — a project is either compliant or it isn't. Economic substance risk is more about the shape of the deal itself: the fee waterfall, the allocation of risk and return among parties, and whether the arrangement would make commercial sense if the tax benefit were stripped out.
For sponsors and buyers, the practical response isn't to avoid complexity, since multi-party structures are common and often necessary. It's to be able to articulate, in plain terms, why the deal is structured the way it is beyond the tax outcome, and to have that rationale documented before an underwriter or an examiner asks for it.