What to Do if You Missed Depreciation on Form 3115

If you forgot to claim depreciation, especially bonus depreciation from a cost segregation study, you might feel like you missed out.

But here’s the truth: with the strategic use of IRS Form 3115, you can not only fix past depreciation errors but potentially supercharge your current-year deductions and receive huge tax savings.

Let’s dive into what to do if you missed depreciation, how cost segregation ties in, and how Form 3115 becomes your golden ticket.

Why Depreciation Is a Big Deal (and Bonus Depreciation Even Bigger)

Depreciation allows you to deduct the cost of your property over time, generally 27.5 years for residential or 39 years for commercial. But cost segregation takes this a step further.

With a cost segregation study, you break out portions of your building (like carpets, appliances, or parking lots) into shorter-life assets (5, 7, or 15 years). Why does this matter?

Because under the old tax law (and now under the OBBBA), you could apply bonus depreciation to these short-life assets, writing off 100% of their value in year one.

If you never performed a cost seg or didn’t apply bonus depreciation properly, you could be sitting on massive missed deductions.

What Happens If You Missed Bonus Depreciation?

Missing out on bonus depreciation means:

• You’re likely paying more taxes today.
• You’re delaying valuable tax deductions.
• You’re still on the hook for depreciation recapture when you sell, whether or not you claimed the deduction.

But here’s where it gets interesting: you can retroactively apply cost segregation and bonus depreciation by filing Form 3115.

Using Form 3115 Strategically with Cost Segregation

Form 3115 (Application for Change in Accounting Method) doesn’t just fix simple depreciation errors like missed straight-line depreciation. It also lets you change how you depreciate assets, including switching from straight-line to accelerated methods or applying missed bonus depreciation.

Here’s how the strategy works:

1. Perform a Cost Segregation Study

First, hire an engineering-based cost segregation firm to analyze your property. They’ll:

• Identify which components qualify for 5-, 7-, or 15-year depreciation.
• Calculate the bonus depreciation you could’ve taken in prior years.
• Provide a detailed report for your tax records.

Example: You bought a $1 million apartment building in 2020. A cost seg study in 2025 reveals that $200,000 of components could’ve been written off immediately with 100% bonus depreciation.

2. File Form 3115 with Section 481(a) Adjustment

Instead of amending past returns, you file Form 3115 under Automatic Change #7.

This allows you to:

• Switch to the correct depreciation method
• Claim the total missed depreciation, including bonus, in the current year as a Section 481(a) adjustment

So in our example, you’d get a $200,000 deduction, less any depreciation already claimed on that portion in prior years, in 2025, instantly lowering your taxable income.

3. Maximize Current-Year Tax Savings

That giant Section 481(a) deduction can:

• Offset rental income and passive gains
• Offset non-passive income if you qualify for the real estate professional status (REPS) or the Short-Term Rental (STR) Loophole.
• Free up cash for reinvestment

Especially for high-income investors, this strategy can create five or six-figure tax savings.

Real-World Example: Bonus Depreciation in Action

Let’s meet Jason, a real estate investor who bought a $2 million commercial building in 2018.

• Without cost segregation, he’s been depreciating the entire building over 39 years.
• In 2025, Jason’s CPA suggests a cost seg study, which identifies $500,000 in 15-year property.
• Because of bonus depreciation, Jason can retroactively apply that bonus.

Using Form 3115, Jason claims a $500,000 (less depreciation already claimed) Section 481(a) deduction on his 2025 return, saving around $150,000 (at the 37% tax bracket).

FAQs

Q: Can I use Form 3115 if I’ve never done a cost segregation study before?

A: Yes! You can apply a new cost segregation study retroactively and catch up depreciation using Form 3115; no need to amend old returns.

Q: How much does a cost segregation study cost?

A: Fees vary, but traditional studies typically range from $5,000–$15,000 depending on property size. The tax savings usually far exceed the cost.

Q: Should I combine cost segregation and Form 3115 without professional help?

A: Definitely not. This is a complex tax strategy involving engineering reports and precise calculations. You need a qualified CPA and a cost seg firm.

Key Takeaways

• Missed bonus depreciation? There’s still time to fix it.
• A cost segregation study plus Form 3115 unlocks retroactive deductions.
• Section 481(a) adjustment delivers the missed depreciation in the current year.
• Professional guidance ensures you get it right and maximize tax savings.

By using this powerful combo, you can transform missed opportunities into major tax wins, putting more cash back in your pocket to grow your real estate portfolio.

Let our expert team handle your Form 3115 and 481(a) adjustments. Contact us today.