Energy Incentives · Guide · Working level
Claiming the Section 179D deduction, start to finish
A 179D claim runs from feasibility screen through energy modeling, site inspection, certification, and — for designers — an allocation letter, before landing on Form 7205. Here is each step, who performs it, how long it takes, and what survives an exam.
Claiming the Section 179D deduction is a six-stage process: a feasibility screen, whole-building energy modeling in DOE-qualified software, a site inspection, a signed certification from a licensed engineer or contractor, an allocation letter if the claimant is a designer rather than the owner, and Form 7205 attached to the return. Building owners then reduce the property's basis by the deduction; designers do not. The whole sequence typically takes two to four months, and every stage generates documentation the IRS will ask for on exam.
The claim at a glance
Each stage has a typical duration and a party responsible for it; the sequence matters because certification cannot precede inspection and Form 7205 cannot precede certification.
| Stage | Responsible party | Typical duration |
|---|---|---|
| 1. Feasibility screen | 179D provider or CPA | 1–2 weeks |
| 2. Energy modeling | Modeler using DOE-qualified software | 3–6 weeks |
| 3. Site inspection | Licensed engineer or contractor | 1–2 weeks to schedule and complete |
| 4. Certification | Qualified individual (licensed in the building's jurisdiction) | 1–2 weeks |
| 5. Allocation letter (designers only) | Authorized representative of the tax-exempt owner | 2–8 weeks, highly variable |
| 6. Form 7205 and return | Taxpayer and return preparer | 1–2 weeks |
The durations compound: an engagement opened in the spring can still miss an extended filing deadline if the allocation letter stalls in a school district's counsel office. Start early.
Stage 1: The feasibility screen
Before anyone builds a model, someone should answer three questions. First, is the building eligible — is it a commercial building or a residential rental building four stories or more, located in the United States, with energy-efficient property placed in service in an open year? Second, is the claimant eligible — the building owner, or a designer of a building owned by a government or (for property placed in service after 2022) any tax-exempt entity? Third, is the deduction worth the study cost — a function of square footage, the applicable per-square-foot rate, and whether prevailing wage and apprenticeship requirements were met to earn the increased rate.
The sunset adds a fourth question as of 2026: did construction of the property begin on or before June 30, 2026? Under the One Big Beautiful Bill Act, Section 179D does not apply to property whose construction begins after that date, so new projects breaking ground now are out regardless of when they are placed in service.
A feasibility screen that skips the eligibility questions and jumps to a fee quote is a red flag about the provider. The screen should also identify which systems — interior lighting, HVAC and hot water, or building envelope — plausibly generate the savings, since that drives modeling scope.
Stage 2: Energy modeling
Section 179D(d) requires energy savings to be demonstrated by modeling the building against a reference building meeting the applicable ASHRAE Standard 90.1 baseline, using software on the Department of Energy's qualified list, published at the DOE 179D program page. The modeler builds two simulations — the building as designed and the ASHRAE reference building — and computes the percentage reduction in annual energy and power costs. Twenty-five percent savings earns the base deduction; each additional percentage point adds to the rate, up to fifty percent.
The applicable ASHRAE version depends on when construction began, which is why the feasibility file should pin down the construction start date with permits or contracts, not recollection. The modeling report should identify the software and version, the ASHRAE baseline applied, the inputs for both buildings, and the resulting savings percentage. A one-page summary with a percentage and no inputs is not a modeling report; it is an exam problem.
Stage 3: Site inspection
The certification requires that a qualified individual has field-inspected the building and confirmed that the energy-efficient property was actually installed as modeled. This is not optional and cannot be done from drawings. The inspector — commonly the same engineer who will sign the certification — walks the building, verifies lighting fixtures, HVAC equipment, and envelope components against the model inputs, and documents the visit with notes and photographs.
Claims certified without a site visit are among the most commonly disallowed. If the provider's process has no travel in it, the certification is defective on its face.
Stage 4: Certification
The certification is a signed statement from a qualified individual — an engineer or contractor licensed in the jurisdiction where the building is located — attesting to the energy savings percentage, the qualified software used, and the inspection. The IRS describes the certification content in its guidance under the energy efficient commercial buildings deduction; the operative requirements trace to Notice 2006-52 as updated for the post-IRA statute.
The certifier is a professional putting a license behind the numbers. Taxpayers should retain the certifier's license information alongside the certificate itself.
Stage 5: The allocation letter — designers only
When the building is owned by a government entity or, for property placed in service after 2022, any tax-exempt organization, the owner cannot use the deduction and may allocate it to the person who designed the energy-efficient property — the architect, engineer, or design-build contractor responsible for the technical specifications. The mechanics, and the fights over who counts as "the designer," are covered in our designer allocation guide; the allocation-letter content requirements for tax-exempt owners are in our tax-exempt allocation brief.
For process purposes, three points. The letter must be signed by an authorized representative of the owner — a title, not just a name, and one with actual authority. The letter must state the amount allocated, and multiple designers on one building cannot collectively exceed the building's maximum. And the letter must exist before the deduction is claimed; a return filed on the strength of a promised letter is a return filed without substantiation.
Stage 6: Form 7205, basis reduction, and the return
For tax years beginning in 2022 and later, the deduction is computed and reported on Form 7205, attached to the claimant's income tax return. The form captures the building's address and square footage, the energy savings percentage, the applicable per-square-foot amount, whether prevailing wage and apprenticeship requirements were satisfied, the certifier's identification, and — for designers — the allocating entity. Our line-by-line walkthrough covers the mechanics.
The tax treatment then diverges by claimant:
Illustrative: assumes 50% modeled savings. Base rate vs. increased rate with prevailing wage and apprenticeship compliance; per-foot amounts are inflation-adjusted annually.
Building owners reduce the basis of the energy-efficient commercial building property by the deduction under Section 179D(e). The property is otherwise 39-year real property, so the deduction effectively accelerates depreciation rather than creating it — the trade discussed in credits versus deductions applies with full force. Owners claiming 179D for a prior year in which the building was already on a filed return generally do so through an accounting method change on Form 3115 rather than an amended return.
Allocated designers own nothing and reduce no basis. The deduction is claimed in the year the property is placed in service, on an original or amended return for that year. Designers should not treat the allocation as taxable income and also claim the deduction; the deduction is the benefit.
Common failure points
Recurring defects, in rough order of frequency: software not on the DOE qualified list, or a version not qualified for the year modeled; no site inspection, or an inspection performed after the certification was signed; allocation letters signed by facilities staff without authority, or letters totaling more than the building maximum across multiple designers; prevailing wage claimed at the increased rate without payroll records; and square footage taken from marketing materials rather than measured or documented sources. None of these is exotic. All are checkable from the file — which is exactly how the IRS checks them.
What to keep for exam
Assemble one file per building, retained for at least the exam window on the claim year: the modeling report and native model files; documentation of the software version's DOE qualification; the signed certification with the certifier's license details; inspection notes and photographs; the executed allocation letter, for designers; certified payroll or equivalent wage records if the increased rate was claimed; construction-start documentation (permits, contracts) supporting both the ASHRAE baseline and, now, the June 30, 2026 sunset test; and the Form 7205 computation workpapers. A claim that can be re-performed from the file is a claim that survives.
Frequently asked questions
- What are the steps to claim the Section 179D deduction?
- A Section 179D claim proceeds through a feasibility screen, whole-building energy modeling in DOE-qualified software, a site inspection by a licensed engineer or contractor, a signed certification, an allocation letter if the claimant is a designer of a tax-exempt building, and finally Form 7205 attached to the return. Building owners then reduce the property's basis; allocated designers include no basis reduction but claim the deduction directly.
- Who signs the Section 179D certification?
- A qualified individual — an engineer or contractor licensed in the jurisdiction where the building sits — signs the certification after field-verifying the energy-efficient property. The certifier must be unrelated to the claimant in the sense of not being the taxpayer claiming the deduction. The certification states the energy savings percentage, the modeling software used, and that the property was inspected.
- How long does a 179D study take?
- A typical Section 179D engagement runs eight to sixteen weeks: one to two weeks for the feasibility screen and document gathering, three to six weeks for energy modeling, one to two weeks to schedule and complete the site inspection, and two to four weeks for certification, allocation-letter execution where required, and Form 7205 preparation. Government allocation letters are often the long pole.
- Does claiming 179D reduce my building's basis?
- Yes, for building owners. Section 179D(e) requires the owner to reduce the basis of the energy-efficient commercial building property by the amount deducted, which reduces future depreciation. Allocated designers do not own the building and make no basis reduction; instead, under current IRS guidance, the designer simply claims the deduction, though older allocations claimed via amended return require care on income treatment.
- What records should I keep for a 179D exam?
- Keep the energy model files and modeling report, the DOE qualified software version documentation, the signed certification, site inspection notes and photographs, the allocation letter with both signatures if you are a designer, prevailing wage and apprenticeship payroll records if you claimed the increased deduction, and Form 7205 workpapers showing the square footage and per-foot computation.