Charleston, SC · $840K
Quadplex, original 1985 build
Year-1 federal benefit
$47,200
Triplex / Fourplex
Fourplex cost segregation: $68K–$165K Year-1 deductions.
Three-to-four kitchens, three-to-four full bath sets, three-to-four HVAC systems — the 5-yr personal-property weight is dense.
The 30-second answer
Triplex and fourplex cost segregation is an engineering-based study that reclassifies a three- or four-unit rental's components out of the default 27.5-year residential schedule into faster 5- and 15-year MACRS classes. Small multifamily reclassifies modestly above a single-family rental — typically 17–21% of building basis — because the unit fixtures are multiplied: three to four kitchens, full bath sets, and HVAC systems, plus the parking, landscaping, and site work. With 100% bonus depreciation the reclassified amount is deductible in Year 1, and a lookback study is especially valuable here; the loss is passive under IRC §469 unless you qualify as a real estate professional or materially participate.
Fourplex cost segregation reclassifies 17–21% of depreciable basis from the 27.5- or 39-year shell into 5-, 7-, and 15-year MACRS classes per 26 U.S.C. § 168 and Rev. Proc. 87-56. Under OBBBA's permanent 100% bonus depreciation (placed-in-service 2025+), reclassified components are deductible in year one. All credible cost-seg providers use the same federal framework — industry-standard 2026 construction cost data, MACRS classification, IRS Audit Techniques Guide (Pub 5653) compliance. What differs across property types is land-allocation share, FF&E weight, and material-participation eligibility under §469.
| Property type | Reclass to 5/7/15-yr | Year-1 federal benefit | Study cost |
|---|---|---|---|
| STR | 23–29% | $55K–$205K | From $495 |
| SFR | 15–20% | $30K–$100K | From $495 |
| Condo | 11–17% | $17K–$61K | From $495 |
| Duplex | 14–19% | $33K–$98K | From $795 |
| Fourplex this page | 17–21% | $68K–$165K | From $795 |
| Office | 17–21% | $100K–$535K | From $1,995 |
| Retail | 21–27% | $105K–$570K | From $1,995 |
| Industrial | 16–20% | $95K–$680K | From $2,495 |
| Self-storage | 20–26% | $170K–$1.3M | From $2,495 |
| Medical office | 16–23% | $95K–$485K | From $2,495 |
| Mixed-use | 12–19% | $71K–$480K | From $1,995 |
| Multifamily | 15–21% | $48K–$150K | From $795 |
| Multifamily 5+ | 15–20% | $120K–$800K | From $1,995 |
| Triplex | 15–19% | $48K–$120K | From $795 |
| Restaurant | 16–24% | $81K–$405K | From $2,495 |
| Vet | 20–26% | $100K–$440K | From $2,495 |
| Gym | 19–35% | $110K–$890K | From $2,495 |
| Dealership | 26–36% | $550K–$3.6M | From $2,495 |
| ADU | 7–12% | $8K–$33K | From $495 |
| Commercial | 18–27% | $105K–$685K | From $1,995 |
| Data center | 45–60% | $3.0M–$31M | $4,995–$54,995 (sub-$100M); $100M+ by proposal |
| Senior living | 20–30% | $340K–$2.0M | By proposal |
Reclassification ranges from internal benchmarks across 4,000+ studies; Year-1 federal benefit assumes 37% bracket and full first-year usability. Study costs are Cost Seg Smart pricing — comparable engineering studies elsewhere range $5,000–$15,000+. See full provider comparison.
Real examples
What fourplex cost seg looks like in practice.
Estimates assume 37% federal bracket and full first-year usability of the loss (active income offset or REPS). Your actual benefit varies with bracket, basis allocation, and CPA's treatment.
Good fit when…
- ✓Triplex/fourplex owners with active income or REPS
- ✓Properties bought 2+ years ago — the lookback math is especially strong here
Skip it when…
- ×Distressed buildings where a major reno is planned (study at the end of reno, not before)
Estimate
Run the numbers on your fourplex.
Pre-set to Fourplex defaults — adjust price + bracket to match your property.
Estimated Year-1 tax savings · Click to order →
$26,640
on $72,000 of accelerated deductions
Want this in writing for your CPA? Get a 1-page analysis →5-yr15-yr27.5/39-yr
Study cost
$995
ROI on study
27×
Delivery
< 1 hour
Estimate based on industry-standard 2026 construction cost data and IRC §168(k). Your actual result varies with property age, condition, and basis allocation.
Frequently asked
Fourplex cost segregation, by question.
Do triplexes and fourplexes qualify for cost segregation?
Yes, and small multifamily reclassifies modestly above a single-family rental — typically 17–21% of basis — because three to four kitchens, bath sets, and HVAC systems multiply the 5-year personal property, on top of the parking and site work. The whole reclassified amount is deductible in Year 1 under 100% bonus depreciation.
I bought my fourplex a few years ago — is it too late?
No, and the lookback math is especially strong on small multifamily. A Form 3115 lookback claims all the missed depreciation in one current-year deduction, with no amended returns, under the IRS automatic-consent procedures.
How much does a triplex or fourplex study cost?
Triplexes and fourplexes are priced on the multifamily 2–4 tier: from $795 for a sub-$300K property, $995 for $300K–$700K, and $1,095 up to $1M, delivered as a CPA-ready PDF in under an hour.
Regulation references
The rules that govern fourplex cost segregation.
- Real estate professional status (REPS) — the 750-hour and 51% tests under 26 U.S.C. § 469(c)(7), and the seven material participation tests under Treas. Reg. § 1.469-5T. Required to offset W-2 income with long-term rental losses unless the property qualifies under the STR loophole.
- Form 3115 (catch-up depreciation) — how to apply cost segregation to a property placed in service in a prior year. Full § 481(a) catch-up adjustment, automatic change-number 7, no IRS user fee.
- Treas. Reg. § 1.469-1T — full reference — all six (A)–(F) exceptions that reclassify a rental as non-rental for passive activity loss purposes.
- Regulations hub — full canonical reference for all cost segregation regulations.
- irsdepreciationrules.com — companion plain-language reference for the underlying IRS depreciation statutes (operated by Cost Seg Smart).
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