CLOSING WINDOW · LOOK-BACK CLAIMS ONLY
Claim what you’ve already earned — before the window closes.
Section 179D and Section 45L have both sunset for new work. What remains is the work already done: qualifying projects that were never claimed, and returns that can still be amended.
★ CURRENT STATUS — PLEASE READ FIRST
Both provisions have terminated for new work.
Section 179D
Terminates for property whose construction begins after June 30, 2026. Projects that broke ground on or before that date remain eligible.
Section 45L
Terminates for homes acquired after June 30, 2026. Homes sold or leased on or before that date remain eligible.
Source: One Big Beautiful Bill Act, Public Law 119-21, enacted July 4, 2025. We will not sell you planning for a provision that no longer applies to new work — but if you have a qualifying past project, there may be real money sitting unclaimed.
★ WHO TENDS TO HAVE UNCLAIMED BENEFIT
The projects that qualified, and were never claimed.
In our experience the gap is rarely eligibility. It is that nobody asked at the time.
Building owners
Commercial property owners who invested in efficient lighting, HVAC or envelope systems and never heard of 179D.
What matters
Efficiency modeling against the applicable standard, plus certification, determines the deduction available.
Architects & engineers
Designers of government-owned and certain tax-exempt-owned buildings who were entitled to an allocation.
What matters
The allocation must come from the building owner. Many firms simply never requested the letter.
Residential developers
Builders who completed and sold or leased qualifying homes and treated the per-unit credit as too small to chase.
What matters
Across a subdivision or multifamily project it is rarely small.
Construction firms
Design-build contractors who carried responsibility for the energy-efficient systems on qualifying projects.
What matters
Eligibility turns on responsibility for the design, not simply on being on site.
★ HOW A LOOK-BACK CLAIM WORKS
Document work, not sales work.
These claims are won or lost on substantiation. Everything below has to exist and hold together before anything is filed — and if it cannot be built, we say so and stop.
Have us look at a project- 01
Establish which projects fall inside the eligible window, by construction start or acquisition date
- 02
Obtain or reconstruct the energy modeling and third-party certification the provision requires
- 03
Confirm the allocation chain where a government or tax-exempt owner is involved
- 04
Quantify the deduction or credit and identify the correct filing mechanism
- 05
Coordinate with your CPA on the amended return or accounting method change
Still eligible at a glance
- Commercial or public buildings where construction began on or before June 30, 2026
- Homes acquired — sold or leased — on or before June 30, 2026
- Amended returns for qualifying prior-year projects, within the statute of limitations
- Designer allocations for qualifying government-owned building projects
★ FREQUENTLY ASKED
Energy deductions after the sunset.
Tax law moves. This page reflects the position as of August 2026; if legislation restores or extends either provision, we will update it here.
No. Under the One Big Beautiful Bill Act (Public Law 119-21, enacted July 4, 2025), Section 179D terminates for property whose construction begins after June 30, 2026, and Section 45L terminates for homes acquired after June 30, 2026. Both dates have passed. We do not market these as forward-looking offerings.
The termination applies prospectively. Commercial and public building projects whose construction began on or before June 30, 2026 may still support a 179D deduction, and homes acquired — sold or leased — on or before that date may still support 45L credits for the eligible contractor. Amended returns and prior-year claims remain available within the ordinary statute of limitations.
It can. For government-owned and certain tax-exempt-owned buildings, the 179D deduction may be allocated to the designer primarily responsible for the energy-efficient systems. Many firms did the qualifying design work and never requested the allocation letter from the owner.
Establishing which projects fall inside the eligible window, obtaining or reconstructing the required energy modeling and certification, confirming the allocation chain where a government-owned building is involved, and coordinating with your CPA on the amended return or accounting method change.
Statutes of limitation do not pause because a provision sunset. Each month that passes closes another tax year to amendment. If you believe you have an eligible project, the window to claim it is narrower than the window to qualify for it ever was.
Then we tell you and we stop. An unsupported energy deduction is not worth the examination risk, and we will not file one.
★ THE WINDOW NARROWS EVERY MONTH
If you have a qualifying project, don’t wait on it.
Send us the project dates and the building type. That is usually enough for us to tell you whether a claim exists.