Why It Matters
You get rental deductions on the rented portion of the property and keep your primary residence exclusion on the unit you live in — and the IRS treats the two portions separately. On a 4-unit where you occupy one unit and rent three, 75% of mortgage interest, property taxes, insurance, repairs, and utilities are deductible rental expenses on Schedule E. That same 75% of the building value is depreciable over 27.5 years. When you sell, the owner-occupied portion qualifies for the $250,000/$500,000 Section 121 exclusion — the rental portion's accumulated depreciation gets recaptured at 25%. Understanding this split is how house hackers turn a primary residence into a tax-advantaged income engine.
At a Glance
- What it is: The dual tax treatment of a house-hacked property — rental deductions on the rented units, primary residence exclusion on the owner-occupied unit
- Allocation formula: Rental Deduction % = Rented Units / Total Units × 100
- Depreciable basis: Rental % × (Purchase Price − Land Value) / 27.5 years
- Section 121 interaction: Owner-occupied unit qualifies for $250K/$500K exclusion; rental portion's accumulated depreciation is recaptured at 25% at sale
- Reported on: Rental income and expenses go on Schedule E; personal portion of mortgage interest and property tax go on Schedule A (if itemizing)
Rental Deduction % = Rented Units / Total Units × 100
How It Works
Expense allocation — the rental percentage does the work. The IRS allocates expenses for a partly personal, partly rental property based on the number of rented units compared to total units. On a 4-unit with you in one unit and tenants in three, the rental percentage is 75% (3 ÷ 4). That 75% applies to every joint expense: mortgage interest, property taxes, insurance, repairs, and utilities. The rental share goes on Schedule E as deductible rental expenses. The remaining 25% is personal — you can deduct the personal portion of mortgage interest and property taxes on Schedule A if you itemize, but you cannot deduct personal-share repairs or insurance.
Depreciation — the building only, and only the rental share. Depreciation under the 27.5-year depreciation rules applies only to the building, not the land, and only to the rental percentage of the building. You must first separate land value from building value (lenders' appraisals typically do this; county assessments are another source). Then apply the rental percentage to the building-only value. That figure divided by 27.5 is your annual depreciation deduction. On a $285,000 building at 75% rental, the depreciable basis is $213,750 — generating $7,773 per year in non-cash deductions that reduce your taxable rental income without reducing your cash flow.
Schedule E reports the whole rental operation. All rental income from your tenants flows to Schedule E. All rental-share expenses — including depreciation — are deducted on Schedule E. The result is your net rental income, which is passive income for tax purposes. If rental expenses exceed rental income, the loss is a passive activity loss subject to the passive loss rules and phase-out thresholds based on AGI. Losses up to $25,000 may be deductible for active participants with AGI under $100,000.
Section 121 interaction — the two portions are treated separately at sale. When you sell the property, the IRS does not blend the owner-occupied and rental portions. Your unit qualifies for the Section 121 exclusion ($250,000 single, $500,000 married filing jointly) as long as you owned and lived in the property for at least two of the five years before sale. The rental units are a different story: all depreciation you claimed — or were allowed to claim — on the rental portion is subject to recapture at a 25% rate (unrecaptured Section 1250 gain). The capital gain beyond recapture on the rental portion is taxed at long-term capital gains rates. This makes keeping accurate records of your adjusted basis and cumulative depreciation essential from day one.
Real-World Example
Jennifer buys a 4-unit building for $380,000. The county appraisal allocates $95,000 to land and $285,000 to the building. She moves into unit 1 and rents units 2, 3, and 4 at $1,000/month each.
Rental percentage: 3 rented ÷ 4 total = 75%
Annual rental income: $1,000 × 3 units × 12 months = $36,000
Deductible rental expenses (at 75%):
- Mortgage interest: $18,240 × 75% = $13,680
- Property tax: $4,800 × 75% = $3,600
- Insurance: $2,400 × 75% = $1,800
- Repairs: $3,200 × 75% = $2,400
- Depreciation: $285,000 × 75% ÷ 27.5 years = $7,773
Total deductions: $13,680 + $3,600 + $1,800 + $2,400 + $7,773 = $29,253
Net rental income on Schedule E: $36,000 − $29,253 = $6,747
That $6,747 is real taxable income — but notice that $7,773 of her deductions is depreciation she never actually paid out. Without depreciation, she would owe tax on $14,520 of rental income. Instead, she owes tax on $6,747. The depreciation shaved off more than half her tax bill on the rental side.
Her personal portion: mortgage interest at $18,240 × 25% = $4,560 and property tax at $4,800 × 25% = $1,200 go on Schedule A if she itemizes — not lost, just treated differently.
At sale, if she has held the property for seven years, she will have claimed approximately $54,411 in cumulative depreciation on the rental portion ($7,773 × 7 years). All of it is subject to the 25% recapture rate — a $13,603 tax bill owed regardless of whether she excluded any gain on the personal unit. She factors that figure into her disposition planning well before listing the property.
Pros & Cons
- Splits the tax treatment intelligently — rental deductions reduce passive income, while the primary residence exclusion protects gain on the owner-occupied unit
- Depreciation generates non-cash deductions that reduce taxable income without reducing cash flow, lowering the effective tax rate on rental income
- Mortgage interest and property taxes on the personal unit remain deductible on Schedule A if itemizing — no expense goes entirely to waste
- Allows new investors to access rental property tax treatment without buying a separate investment property
- Depreciation recapture at 25% at sale is unavoidable — even if the investor never claimed depreciation, the IRS recaptures the "allowed or allowable" amount
- Passive loss rules limit deductibility of rental losses above a $25,000 threshold for high earners; investors with AGI above $150,000 lose the allowance entirely
- Accurate expense tracking is mandatory — mixed personal/rental expenses require proportional allocation, and sloppy records create audit exposure
- Section 121 exclusion does not cover the rental portion of the gain, so the dual treatment requires more complex tax preparation at disposition
Watch Out
The "allowed or allowable" trap. Many investors skip depreciation because they fear recapture. The IRS does not allow this strategy: at sale, they recapture the depreciation you were allowed to take, whether or not you actually took it. If you owned the 4-unit for 10 years and never claimed depreciation on the rental portion, the IRS still charges the 25% recapture rate on $77,730 worth of depreciation ($7,773 × 10 years). Take the deduction — you pay the same tax either way.
Land must be separated from the depreciable basis. If you do not carve out land value, you will over-depreciate the property, which creates a larger recapture bill at sale and potential penalties. Use the lender's appraisal, the county assessor's allocation, or a cost segregation study to establish land value at purchase.
Changing from personal to full rental use resets the calculation. If you stop living in the property and rent all units, the allocation shifts to 100% rental. The new depreciable basis is recalculated from that date. And when you sell, the Section 121 exclusion still applies to your unit proportionally — but only for the years you actually lived there. Track occupancy dates carefully.
Passive loss phase-outs hit at $100K AGI. The $25,000 rental loss allowance for active participants phases out between $100,000 and $150,000 AGI. Once AGI exceeds $150,000, rental losses are suspended and carry forward to offset future passive income or gains at sale. Know where your AGI lands before projecting the annual tax benefit.
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The Takeaway
House hacking is one of the few strategies where you can claim rental expense deductions and depreciation on a significant portion of your primary residence while still protecting your personal unit under the Section 121 exclusion. The allocation formula is straightforward — rented units divided by total units — and it applies consistently to every shared expense. What makes the strategy complicated is the exit: depreciation recapture on the rental portion is mandatory, the two portions of the property are treated separately at sale, and your adjusted basis must be tracked from day one. Get the numbers right going in, report them consistently on Schedule E, and work with a CPA who understands mixed-use residential property before your first tax filing.