Cost Segregation: When It Actually Works

TL;DR

• Cost segregation is an engineering study that reclassifies building components from 27.5-year to 5-, 7-, or 15-year depreciation — creating larger deductions earlier.
• Combined with bonus depreciation, it can generate very large first-year deductions. But those deductions only help if you can use them against taxable income (passive loss rules apply).
• On sale, every dollar of accelerated depreciation taken creates a dollar of depreciation recapture — taxed at 25%. Model the exit before optimizing the entry.

What cost segregation does

Standard residential depreciation: building value ÷ 27.5 years (straight-line). On a $400,000 building, that is $14,545/year.

Cost segregation reclassifies specific components into shorter lives under MACRS (Modified Accelerated Cost Recovery System):

A typical residential rental might have 15–30% of the purchase price (building portion) reclassified to 5/7/15-year property through cost segregation.

Bonus depreciation: the multiplier

IRC §168(k) allows qualified property to be expensed immediately in the year placed in service, rather than depreciated over its asset life. Property reclassified through cost segregation typically qualifies.

Bonus depreciation rates (post-TCJA, OBBBA 2025):

• 2023: 80%
• 2024: 60%
• 2025: 40%
• 2026: 20% (currently scheduled)
• 2027+: 0% (unless extended)

Verify the current rate at IRS.gov. Congress has extended bonus depreciation multiple times — the rate may change.

Combined effect (2025): $400,000 property, 25% of building value reclassified = $75,000 of short-life property. At 40% bonus depreciation, $30,000 is expensed immediately. The remaining $45,000 is depreciated over 5/7/15 years (still faster than 27.5). First-year deduction increase vs. standard depreciation: significant.

The economics: when does a study make sense?

A cost segregation study costs $5,000–$15,000 for a typical residential rental. The NPV calculation:

Study makes sense if:

• Additional first-year deductions × your marginal tax rate > study cost + time value
• You can actually use the deductions (passive loss rules, STR/REP qualification)
• The property value is large enough to justify the reclassification analysis

Minimum property value for cost segregation to pay:

• With passive loss qualification (STR/REP): $300,000+ property value
• Without passive loss qualification (deductions suspend): NPV of deferred deductions may not justify the study cost — run the numbers

Example: $600,000 property, 20% reclassified to short-life property = $120,000 at 40% bonus depreciation = $48,000 immediate deduction. At 37% marginal rate (and qualifying for STR): $48,000 × 37% = $17,760 in year-one tax savings. Study cost: $8,000. Net benefit in year one: $9,760 — and additional accelerated deductions in years 2–5.

Without STR/REP qualification: the $17,760 tax savings is deferred — you do not realize it until you have passive income or sell.

Depreciation recapture: the exit cost

Every dollar of depreciation you take reduces your cost basis. On sale:

• The IRS taxes accumulated depreciation deductions at 25% (unrecaptured §1250 gain rate) — not the LTCG rate
• This applies to all depreciation, including cost-segregated amounts
• It cannot be avoided through a 1031 exchange (it defers) or through holding

Example: You take $200,000 in total depreciation over 10 years (standard + cost segregation). On sale, $200,000 of recapture is taxed at 25% = $50,000 in recapture tax.

Step-up in basis at death eliminates this recapture permanently — for heirs. During your lifetime, recapture is a real liability.

Model this before buying. Many cost segregation presentations show year-one deductions without showing the recapture liability on exit. You need both numbers.

Cost segregation look-back study

If you purchased a property in a prior year without doing cost segregation, you can do a look-back study now and claim the missed accelerated deductions in the current year without amending prior returns. (IRS Rev. Proc. 2011-14)

This creates a “catch-up” deduction in the current year for all the accelerated depreciation you could have taken since purchase. Useful if your qualification status has changed (e.g., spouse now qualifies for REP status).

What most content gets wrong

“Cost segregation is free money.” The deductions are real but deferred — not free. Every accelerated deduction taken today creates a proportional recapture liability on exit. The benefit is the time value of deferral, not permanent elimination.

“Everyone should do cost segregation.” It is only worth doing if (a) the study cost is justified by the property size, and (b) you can use the deductions currently. For most W-2 earners above $150k without STR/REP qualification, the deductions sit as suspended passive losses — the time value of deferral may not justify a $10,000 study fee.

“You must do it in year one.” You can do a look-back study later if your situation changes. Do not rush a cost segregation study just because you recently purchased — first confirm you can use the deductions.

Decision checklist

Before commissioning a cost segregation study:

• Is the property value above $300,000?
• Do you currently qualify for STR material participation or REP status?
• If not, when do you expect to qualify — and what is the NPV of deferred deductions vs. study cost?
• Have you modeled the depreciation recapture liability on your expected exit price?
• What is the current bonus depreciation rate? (Verify at IRS.gov)
• Has a CPA reviewed whether your specific property type qualifies for reclassification?
• Is this a year where accelerated deductions would be most valuable (high income year, offsetting a large gain)?

When to call a CPA and an engineer

Cost segregation requires both a cost segregation engineer (who performs the physical analysis) and a CPA (who confirms qualification, reviews the study, and applies it correctly to your return).

Do not commission a cost segregation study without CPA involvement in the process. Engineering firms have incentive to maximize the reclassification — your CPA ensures the positions are defensible on audit.

Sources

• IRC §168 — Modified Accelerated Cost Recovery System (MACRS)
• IRC §168(k) — Bonus depreciation
• IRC §1250 — Unrecaptured §1250 gain (depreciation recapture at 25%)
• IRS Rev. Proc. 87-56 — Asset class lives for MACRS
• IRS Audit Technique Guide — Cost Segregation (2023 edition)
• IRS Rev. Proc. 2011-14 — Automatic consent for cost segregation look-back studies