Form 3115 Change Number 152: Catching Up on Old 179D Deductions

TL;DR: If you own a commercial building that qualified for the 179D energy efficient building deduction and nobody ever claimed it, you may be able to claim it now on your current return with Form 3115, without amending old returns. The automatic accounting method change for 179D carries designated change number 152. Designers who received a 179D allocation cannot use this route. A 179D deduction reduces the building's basis, so it has to be coordinated with any cost segregation catch-up on the same building.

Can you still claim a 179D deduction you missed?

Often, yes, if you own the building. 179D generally applies to qualifying property placed in service after December 31, 2005. If you own an office, warehouse, retail building, or an apartment building tall enough to fall under the ASHRAE 90.1 energy standard (generally four or more stories above ground), and its lighting, HVAC and hot water systems or building envelope were certified as qualifying, a deduction you never took may still be available. For who qualifies in the first place, see who qualifies for the 179D deduction now that the sunset has passed.

The IRS treats the missed deduction as a change in accounting method, not as a math error. That means you claim it with Form 3115 on a current return. The catch-up is the one deduction you missed in the year the property went into service, adjusted for any depreciation you already took on the same cost.

Two limits matter. Buildings placed in service in 2022 or earlier are held to the older rules: the IRS 179D page says the deduction for those years is "Capped at $1.80 per square foot." And you still need the energy certification that 179D requires, prepared by a qualified individual.

How does Form 3115 work for a 179D look-back?

It is an automatic accounting method change. Rev. Proc. 2012-39 added it to the IRS list of automatic changes and said "The designated automatic accounting method change number for a change in method of accounting under section 8.04 of this APPENDIX is '152.'" The current list of automatic changes, Rev. Proc. 2025-23, carries the 179D change in section 8.01.

Why does change number 152 matter?

It tells the IRS which automatic change you are making. The Form 3115 uses designated change number 152, and because the change is automatic, there is no user fee and no request for advance consent. One eligibility rule to check first: under Rev. Proc. 2015-13, the automatic route is generally unavailable if you changed your method for the same item within the past five years.

Because the adjustment is in your favor, Rev. Proc. 2015-13 section 7.03(1) puts all of it in "one taxable year (year of change) for a negative § 481(a) adjustment." The missed deduction lands on one return, including deductions from years that are already closed to amendment.

What are the limits on a 179D catch-up?

Can designers use Form 3115 for a 179D allocation?

No. Rev. Proc. 2012-39 says "This change does not apply to a designer to whom the owner of a government building allocates the § 179D deduction." The reason is that a designer never depreciates the building, so there is no accounting method to change. A designer who missed an allocated deduction has to look at amending the return for the year the building was placed in service, while that year is still open.

Can you claim 179D twice on the same work?

No. If 179D was already claimed on an improvement, there is nothing left to catch up on for that work. The IRS 179D page also says "Expenses deducted in the prior 3 years (4 years for an allocated deduction) reduce the maximum deduction" for a later project on the same building.

A new project is a separate question, and the window for new work is closing. Section 179D(i), added by the One Big Beautiful Bill Act, says "This section shall not apply with respect to property the construction of which begins after June 30, 2026." A later retrofit can qualify on its own only if construction on it began by that date. That cutoff is the subject of our episode on claiming 179D on a building you have owned for years.

Can you combine 179D with cost segregation?

Yes, and on an older building they work well together. A cost segregation study moves 5, 7 and 15-year property out of the 39-year building. 179D covers systems that usually stay in the 39-year class: interior lighting, HVAC and hot water, and the building envelope. Both depend on an engineering review of the same building, with a trained professional on site.

They have to be coordinated, though. Section 179D(e) says "the basis of such property shall be reduced by the amount of the deduction so allowed." If you run a cost segregation look-back and a 179D catch-up on the same return, the depreciation catch-up has to be figured on the reduced basis, or the same dollars get deducted twice. Your preparer should build both adjustments together.

Is a 179D look-back worth checking?

If you own a commercial building placed in service after 2005 and nobody ever looked at 179D, yes. The deduction you missed may still be recoverable on one current return, and the review can run alongside a cost segregation look-back on the same building.

The no-cost analysis tells you whether a building you own has a real shot at 179D, and what a cost segregation look-back would add, before you commit to anything. No obligation and no pitch. If a study will not pay for itself, I will say so. Book a time at calendly.com/david-wiener/cs or call 770-224-8504, option two. Cost segregation, 179D and R&D credit studies are delivered through my relationship with CSSI (Cost Segregation Services, Inc.).

This article is educational and is not tax, legal, or accounting advice. Every situation is different; work with a qualified tax professional before acting on any strategy described here.