Five fully worked examples of Form 3115 §481(a) catch-up adjustments — the same five properties summarized in the homepage table, expanded with the full underlying math. Each example shows the property, basis allocation, reclassification by life class, prior-year depreciation taken, the §481(a) catch-up calculation, and the final federal tax savings.
Numbers are realistic estimates from the same engine that powers the homepage calculator. Your specific results will depend on cost basis allocation, location-specific cost benchmarks, and your CPA's review. These examples assume bonus depreciation rates per the IRS phase-down schedule (100% for 2018–2022, 80% for 2023, 60% for 2024, 40% for 2025).
Example 1: Phoenix duplex (long-term rental)
| Property | Phoenix duplex, 2,400 sqft total, two units |
|---|---|
| Purchase | $500,000 in March 2021 |
| Land | $100,000 (20%) |
| Building basis | $400,000 |
| Tax bracket | 32% |
| Years held | 4 (placed 2021, lookback in 2025) |
Engineering reclassification: 22% of building basis into accelerated buckets. 5-year personal property (carpets, appliances, wall coverings): $40K. 15-year land improvements (driveway, landscaping, exterior lighting): $48K. Remaining $312K stays in 27.5-year residential.
What was actually deducted (straight-line): 2021 partial-year + 3 full years ≈ $54.5K total.
What should have been deducted (cost seg with 100% bonus on 2021 placed): Year 1 = $40K + $48K + $9.5K residential = $97.5K. Years 2–4 residential only = $34K. Total = $131.5K.
§481(a) adjustment: $131.5K − $54.5K = $77K. (The homepage estimate of $87K assumes a slightly higher reclassification — 24% — reflective of typical engineering capture.) Tax savings at 32% ≈ $25K–$28K.
Bottom line: Strong YES verdict. The 100% bonus rate from 2021 makes this lookback particularly powerful.
Example 2: Nashville STR cabin (short-term rental)
| Property | Nashville cabin, 3-bedroom, fully furnished STR |
|---|---|
| Purchase | $750,000 in May 2022 |
| Land | $150,000 (20%) |
| Building basis | $600,000 |
| FF&E (furniture, appliances) | $80,000 separately captured |
| Tax bracket | 35% |
| Years held | 3 (placed 2022) |
Engineering reclassification: STRs capture more 5-year personal property than long-term rentals because furnishings, kitchenware, and decor count. 30% of building basis lands in 5-year/15-year accelerated buckets. 5-year personal property (FF&E + interior soft goods): $108K. 15-year land improvements (deck, hot tub pad, fire pit): $72K. Remainder $420K residential.
Actually deducted (straight-line, plus separate FF&E depreciation): $48K total across 3 years.
Should have been deducted (100% bonus on 2022 placed): $108K + $72K + 3 yrs of residential straight-line ($45K) + bonus on FF&E = $206K total.
§481(a) adjustment: ~$158K. Tax savings at 35% = $55K.
STR-specific note: Material participation (or short-term-rental treatment under IRC §469(c)(7)) is required to use the deduction against W-2 income. Without it, the loss is suspended (passive). Your CPA should confirm this treatment.
Example 3: Austin commercial office
| Property | Austin Class-B office, 8,500 sqft, multi-tenant |
|---|---|
| Purchase | $1,200,000 in November 2020 |
| Land | $300,000 (25%) |
| Building basis | $900,000 |
| Tax bracket | 37% |
| Years held | 5 (placed 2020) |
Engineering reclassification: Commercial properties capture more reclassifiable basis (typically 25–35%) because of HVAC zone systems, specialty electrical for office equipment, partition walls, and tenant fit-out. 30% reclass: 5-year property (carpet, partitions, decorative lighting): $135K. 15-year property (parking lot, exterior signage, irrigation): $135K. Remainder $630K commercial 39-year.
Actually deducted (straight-line over 39 years): $115K total across 5 years.
Should have been deducted (100% bonus on 2020 placed): $270K immediate bonus + 5 yrs of residential = $345K total.
§481(a) adjustment: ~$230K. Tax savings at 37% = $85K.
Commercial note: Office and retail are top-of-the-list candidates for lookback because the 39-year straight-line baseline means even moderate reclassification produces large catch-ups.
Run the calculator on the homepage to see your estimated Year-1 catch-up deduction and federal tax savings before you commit to a study.
Run the calculator Order a lookback studyExample 4: Suburban single-family rental (modest catch-up)
| Property | Suburban Atlanta SFR, 1,800 sqft, long-term rental |
|---|---|
| Purchase | $320,000 in August 2019 |
| Land | $64,000 (20%) |
| Building basis | $256,000 |
| Tax bracket | 24% |
| Years held | 6 (placed 2019) |
Engineering reclassification: 18% reclass (lower for plain-vanilla SFR than for STR or commercial). 5-year property: $25K. 15-year land improvements: $20K. Remainder $211K residential.
Actually deducted: ~$56K straight-line over 6 years.
Should have been deducted (100% bonus 2019): $45K bonus year 1 + 6 yrs residential ($46K) = $91K.
§481(a) adjustment: ~$42K. Tax savings at 24% = $10K.
Honest read: A $10K savings on a $495 study fee is still a 20× ROI — but the absolute dollars are modest because the bracket is lower and the property is smaller. This is the floor of "still worth doing." Below this scale (sub-$200K building basis, sub-24% bracket), the math gets thin.
Example 5: Sedona STR with 2025 reduced bonus
| Property | Sedona STR, 2,100 sqft, hot tub + outdoor kitchen |
|---|---|
| Purchase | $620,000 in February 2021 |
| Land | $124,000 (20%) |
| Building basis | $496,000 |
| Tax bracket | 32% |
| Years held | 4 (placed 2021) |
Engineering reclassification: 28% reclass. 5-year FF&E + interior: $89K. 15-year land improvements (hot tub deck, fire pit area, outdoor kitchen base): $50K. Remainder $357K residential.
Actually deducted: ~$67K straight-line over 4 years.
Should have been deducted (100% bonus 2021): $139K bonus year 1 + 4 yrs residential ($52K) = $191K.
§481(a) adjustment: ~$134K. Tax savings at 32% = $43K.
Why the placed-in-service year matters so much: If this same property had been placed in 2025 instead of 2021, the bonus rate would be 40%, not 100%. The catch-up would shrink to roughly $80K instead of $134K — a $20K difference in tax savings. This is why we say pre-2023 properties produce the largest lookback values.
What these examples have in common
- Tax bracket matters more than people expect. The 24% Atlanta SFR vs 37% Austin office example: same engineering effort, very different absolute dollars.
- Placed-in-service year is a free lever. 100% bonus years (2018–2022) produce 1.5–2× the catch-up of 2024–2025 placements.
- Property type drives reclass percentage. Plain SFR ≈ 18%, STR ≈ 28%, Commercial ≈ 30%. STRs and commercial are best-in-class.
- The catch-up is always larger than a forward-only study. In all five cases, doing cost seg now (lookback) produces a Year-1 deduction 3–5× larger than starting cost seg on a fresh property at today's 40% bonus rate.
Bottom line
The catch-up math is mechanical — it depends on basis, reclassification %, bonus rate at placement, years missed, and your bracket. Run the homepage calculator with your numbers. If the result lands above $30K of tax savings, the math almost always justifies a $495–$1,895 lookback study. Read the Form 3115 filing guide next.