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Last updated: August 7, 2026
The construction-start deadline for new 179D projects passed on June 30, 2026. That doesn't mean the deduction is closed for everyone. If you placed a qualifying building in service in recent years and never claimed 179D, you may still have time.
Why this matters right now
Why this matters right now
179D isn't claimed automatically. Plenty of building owners install qualifying lighting, HVAC, or envelope upgrades and never realize the deduction was available, because their CPA didn't flag it or no one ran the energy model to prove eligibility.
If that's your building, the sunset doesn't affect you. Sunset applies to when construction begins on new projects. It doesn't erase deductions available for buildings already placed in service.
What you need to check
What you need to check
Was the building placed in service after 2005? 179D applies to a broad window of construction and renovation activity, not just recent years.
Did the project include lighting, HVAC, hot water, or building envelope upgrades? These are the three system categories that qualify.
Has an energy model ever been run on this building? If not, this is the first step. Without it, there's no way to know if you qualify or how much you're eligible for.
Do you still have access to construction documents, equipment specs, or as-built drawings? Certification requires this kind of documentation. The older the project, the harder it can be to locate.
Designers: don't assume you're out of luck either
Designers: don't assume you're out of luck either
If you're an architect, engineer, or contractor who designed a school, library, government building, or nonprofit facility, and the building owner never allocated the 179D deduction to you, that allocation may still be available depending on timing. This is worth checking project by project.
What this looks like in practice
What this looks like in practice
A retroactive claim typically involves:
A review of which buildings in your portfolio (or your project history, if you're a designer) might qualify
An energy model or certified analysis to establish the deduction amount
Coordination with your CPA to file an amended return within the statute of limitations
This isn't a new-construction incentive anymore. It's a documentation and deadline problem. That's a different kind of work, but it's real money still on the table for buildings that already exist.
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