Why This Deadline Is Different From Past BOC Windows
Developers have navigated beginning-of-construction determinations before, and for years the 5% Cost Safe Harbor gave projects a straightforward path: spend 5% of total project cost and the construction-start clock effectively started. Notice 2025-42 removed that safe harbor for the purpose of the OBBBA's wind and solar termination analysis. What's left is the physical work test, which asks whether work of a significant nature actually happened on-site or on manufactured components, not whether money changed hands.
That's a meaningfully higher bar. A signed contract and a deposit used to be enough groundwork. Now the IRS has specifically flagged that it will scrutinize artificial acceleration of construction-start dates, which means a project claiming a pre-deadline start needs to show real, physical evidence: dated site photographs, equipment mobilization logs, contractor sign-in records, and a written description of the work performed.
The Two Deadlines Developers Keep Conflating
There's a second layer of complexity that's tripping people up. The July 4, 2026 date governs whether a wind or solar project can claim the credit at all under the termination provisions. It's a separate question from the FEOC beginning-of-construction determination, which governs whether a project falls under the material assistance rules. As we covered in the 2026 supply chain trap breakdown on surviving FEOC limits and the Direct Pay haircut under Section 48E, the FEOC BOC rules still reference the 5% Cost Safe Harbor under Notice 2013-29 and Notice 2018-59, pending separate Treasury guidance. That means a project could satisfy one construction-start test using the safe harbor while needing to satisfy the other using the physical work standard. Treating both deadlines as one calculation is how projects end up with a construction-start position that only survives half of the analysis it needs to survive.
What Actually Counts as Physical Work
The physical work test isn't about spending thresholds, it's about activity. Site excavation, foundation pouring, and the installation of racking or mounting structures typically qualify. So does off-site manufacturing of components specifically designed for the project, provided that work is documented as connected to the specific facility rather than general inventory production. What doesn't qualify: preliminary activities like permitting, site surveys, financing arrangements, or clearing land without further construction activity. A project that has only completed these preliminary steps by July 4 has not established a construction start under this standard, regardless of how much has been spent.
Documentation That Holds Up Under Scrutiny
Given the IRS's stated intent to examine these determinations closely, the documentation standard should be built for an audit, not just for a closing binder. That means time-stamped photographs showing work in progress, not just a completed pour. It means equipment delivery and mobilization records tied to the specific project site. It means contractor logs that show continuous, genuine activity rather than a single day of token work designed to establish a date. For projects also relying on Section 48E, this same construction-start determination interacts with the domestic content and prevailing wage requirements discussed in the Section 48E Complete Guide for 2026, so the underlying documentation package should be built once and used to support every dependent determination, rather than assembled separately for each requirement.
What to Do With the Time That's Left
For projects that haven't yet established a documented construction start, the practical move is to get real physical work underway immediately and to build the evidentiary record as the work happens, not after the fact. For projects that believe they've already cleared the bar, this is the moment to have counsel review the documentation against the physical work standard specifically, not against the 5% safe harbor standard that no longer applies to this determination. The credit consequences of getting this wrong aren't a reduction. They're a full loss of eligibility, which makes this one of the highest-stakes compliance questions active in the market right now.