If your firm has designed schools, courthouses, municipal buildings, universities, military facilities or public housing, you have almost certainly created deductions you never claimed.
Section 179D rewards energy-efficient commercial buildings. When the owner is a government body or another tax-exempt entity, they have no tax liability to apply it against — so the law lets them allocate the deduction to the designer instead. To the architect, the engineer, the design-build contractor who wrote the technical specifications.
Most design firms have never asked for one. And unlike building owners, whose window on this stays open for decades, yours closes a year at a time.
Two Clocks, Both Running
The statute of limitations. A designer claims by amending the return for the year the building was placed in service — generally within three years. Every filing season, another year of your project history becomes unrecoverable.
The program itself. Section 179D terminated for property where construction begins after 30 June 2026. New allocations will keep arriving for a while as projects already underway complete, but the pipeline is now finite and shrinking.
This is not a “we’ll get to it next year” item. Next year, part of it is gone.
What an Allocation Actually Is
The building owner signs an allocation letter assigning the 179D deduction for that property to you. It isn’t automatic and it isn’t your right — the owner decides. Which means the work has two halves: qualifying the building technically, and getting the letter.
The second half is usually the harder one, and it’s the reason most firms never start. A school district business office has no particular reason to prioritize your tax paperwork. Firms that do this well build the request into project closeout rather than chasing letters years later from people who’ve moved on.
Are You a Designer?
The term has a specific meaning. A designer is a person who creates the technical specifications for installation of energy-efficient commercial building property — the lighting, the HVAC and hot water systems, or the building envelope.
| Typically a designer | Typically not |
|---|---|
| Architects | Contractors who only install to someone else’s specifications |
| Engineers — mechanical, electrical, lighting | Firms that only repair or maintain |
| Design-build contractors | Material and equipment suppliers |
| Energy services providers and ESCOs | Construction managers with no design responsibility |
| Environmental and energy consultants who specify systems |
More than one designer can be involved in a single building — the architect and the MEP engineer, for example. The owner can allocate among them, and the allocation has to be sorted out between the parties rather than assumed.
The Vintage Rule That Decides Half of Your Backlog
This is the detail most firms get wrong when they go looking, and it will save you from chasing the wrong projects.
| Placed in service | Who could allocate to a designer | Deduction ceiling |
|---|---|---|
| Through 2022 | Government building owners only — federal, state, local, including schools and public universities | $1.80 per square foot lifetime per building, inflation-indexed after 2020, available in partials of roughly $0.60 per system |
| 2023 onward | Government owners plus other tax-exempt entities — private universities, hospitals, non-profits, tribal governments | Roughly $0.58 to $5.81 per square foot, scaled by energy savings and by whether prevailing wage and apprenticeship requirements were met |
So a private hospital you designed in 2020 could not allocate to you. The same client in 2023 could. When you pull your project list, sort by year before you sort by anything else.
One More Constraint on Repeat Work
The per-building cap is reduced by amounts deducted in the prior three tax years — or over a four-year period ending with the year in question where the deduction went to someone other than the building owner, which is exactly the designer allocation case.
Practical effect: if you’ve done multiple phases on the same campus building, or another designer already claimed on it, your available amount is constrained by that history. Allocations have to be modelled building by building, not year by year.
Designers Cannot Use the Shortcut Owners Have
You may have read that 179D can be caught up on a current-year return using Form 3115, reaching back as far as 2006 with no amended returns. That is true — for building owners.
It is expressly not available to designers. The automatic accounting-method change excludes a designer to whom a building owner allocated the deduction, and the Second Circuit confirmed it in 2025: a designer’s 179D deduction is a one-time allocated deduction that permanently reduces taxable income, not a timing item — so there is no accounting method to change.
Your route is an amended return for the placed-in-service year, with Form 7205. Which is why your window is three years and not twenty, and why anyone selling you a two-decade designer look-back is selling you something that doesn’t exist.
What the Work Involves
179D requires certification by a qualified individual, supported by approved energy modeling software and, in most cases, a site visit. It is an engineering deliverable, not a spreadsheet estimate — and that’s what makes it hold up.
For a design firm the sequence is usually: pull the project list, screen by year and owner type, model the likely qualifiers, request allocation letters, certify, then amend. The modelling tells you which letters are worth chasing, so it comes before the awkward phone calls rather than after.
Send Three Columns
What we’ll need: Project name · Year placed in service · Owner type — government, tax-exempt, or private
We’ll tell you which projects are still inside the amendment window, which owner types could allocate in that year, and which are worth modelling. No cost to find out which ones aren’t.
Frequently Asked Questions
The building owner won’t sign. Can we still claim?
No. The allocation from the owner is the foundation of a designer’s claim. If the letter doesn’t exist, there’s nothing to claim — which is why the request belongs in project closeout, while your client contact still works there and still remembers you.
Does the 30 June 2026 date affect projects we already designed?
No. That date governs when construction could begin on new projects. Buildings already placed in service are unaffected — your constraint on those is the amendment window, not the termination date.
What exactly did “beginning of construction” mean for 179D?
Honestly, Treasury never defined it for this section. The statute doesn’t define it and doesn’t cross-reference anything that does. Practitioners analogize to standards developed for other energy provisions, but that’s an analogy rather than authority — and one widely cited notice on the subject applies to entirely different Code sections. If you have a project near the line, document the start thoroughly and take advice, and be sceptical of anyone stating the test with more confidence than the guidance supports.
We’re a subconsultant, not the prime. Does that matter?
Not by itself. What matters is whether you created the technical specifications for the qualifying systems. An MEP engineer under an architect prime is frequently the designer of record for the systems that actually drive the energy model.
Our buildings weren’t designed to be “green.” Is it worth looking?
Frequently, yes. Public buildings are often built to energy codes that clear the thresholds without anyone setting out to design a green building — and lighting-only partial deductions were available under the pre-2023 rules and are the most commonly missed. The only way to know is to model it.
Does this affect our financial statements or our indirect rates?
It’s an income tax deduction. Worth raising with your accounting team as part of the engagement, particularly for firms on government contracts, but it is not a change to your cost structure.
What to Do Next
Send the project list with years and owner types. The screen is quick, and the answer determines whether this is a conversation about three projects or thirty.
If the answer is that your window has already closed on most of them, we’ll tell you — and we’ll tell you how to make sure it doesn’t happen again on the ones still in design.
This article is general information about federal tax rules and is not advice for any specific situation. Eligibility depends on the building, the owner, the year placed in service, the allocation and your firm’s role, all of which must be examined individually.
Current as of September 2026.
