Why basis matters so much
Your tax basis in a rental property is the starting point for calculating taxable gain when you sell. Gain = amount realized (sale price minus selling costs) minus adjusted basis. The lower your adjusted basis, the higher your taxable gain — which means more capital gains tax and more depreciation recapture. A well-tracked basis that includes every legitimate dollar of cost can save tens of thousands of dollars at sale.
Adjusted basis also matters for: calculating your annual depreciation deduction (you can only depreciate your depreciable basis, i.e., cost allocated to the building); determining your loss if you sell at below your basis; computing gain or loss in a 1031 exchange; and calculating the inherited step-up or gift carryover when property changes hands without a sale.
Because basis affects so many calculations that extend across years or decades of ownership, the time to start tracking it is the day you buy — not the day before you sell when your accountant scrambles to reconstruct records.
Step 1: Establish your initial basis at purchase
Your initial basis in a purchased property is generally the purchase price — the amount you agreed to pay. But initial basis also includes most costs you paid at closing: title search fees, attorney fees, recording fees, surveys, and transfer taxes paid by the buyer. It does NOT include amounts the seller paid (though they may reduce the price) or amounts you financed through escrow for prepaid property taxes or homeowners insurance (those are deductible expenses, not basis adjustments).
Closing cost items that add to basis include: abstract fees, recording fees, surveys, title insurance (owner's policy), legal fees to secure title, and transfer taxes in jurisdictions where the buyer pays them. Items that do not add to basis include: loan origination fees (these are separately amortized), prepaid insurance, prepaid property taxes, and homeowners association dues.
Example: You buy a rental for $350,000. Closing costs include: title insurance $1,200, attorney fee $800, recording fee $150, survey $400, county transfer tax (buyer pays) $700. Initial basis = $350,000 + $1,200 + $800 + $150 + $400 + $700 = $353,250.
Step 2: Allocate between land and building
Land is not depreciable — you can only depreciate the building (and certain improvements). At purchase, you must allocate your initial basis between land and building. The most defensible method is to use the county assessor's land-to-improvement ratio from the property tax assessment. If the assessor values land at 25% and improvements at 75% of the total, apply those percentages to your cost basis.
Using the $353,250 basis above with a 25% land / 75% building split: land basis = $88,313; building basis = $264,937. Only the building basis ($264,937) is depreciable over 27.5 years, giving a first-year depreciation deduction of roughly $9,634 per year ($264,937 ÷ 27.5), with a slight reduction in year one from the mid-month convention.
Keep a copy of the county assessment printout that supports your land/building allocation in your permanent tax files. If audited, you need to explain why you put X% to land and Y% to building. An assessor's ratio is objective and defensible. Appraisal allocations or purchase price allocations from the closing (if stated in the contract) are also usable.
Step 3: Track capital improvements over the years
Every capital improvement you make to the property adds to your basis. Capital improvements are expenditures that: add to the property's value, appreciably prolong its useful life, or adapt it to a new use. They are distinguished from ordinary repairs (which are currently deductible) and are themselves generally depreciated over their applicable recovery period.
Common capital improvements that increase basis: a new roof (27.5-year property or shorter if a separate component), HVAC system replacement, kitchen or bathroom remodel, addition of a deck or garage, new flooring, landscaping that adds value, installation of a new fence or driveway, and addition of a swimming pool. Routine repairs — fixing a leaky faucet, painting, patching drywall — are not capital improvements and do not increase basis.
The Tangible Property Regulations (TPR) from 2013 provide safe harbors that let landlords expense certain improvements that would otherwise be capitalized. The de minimis safe harbor allows expensing items costing $2,500 or less per invoice (or $5,000 with an applicable financial statement). The small taxpayer safe harbor can allow expensing of building improvements up to the lesser of $10,000 or 2% of the unadjusted basis per year. Items expensed under these safe harbors are deducted currently and do NOT increase basis.
Build a property improvement ledger: a simple spreadsheet with columns for date, description, amount, and whether you expensed it or capitalized it. Capitalized items also need their own depreciation start date and recovery period.
Step 4: Subtract depreciation to get adjusted basis
Every year you claim (or could have claimed) depreciation, it reduces your adjusted basis. The IRS rule is "allowed or allowable" — you reduce basis by the depreciation you actually claimed or, if you forgot to claim it, the depreciation you were entitled to claim. Forgetting to depreciate does not preserve your basis; it forfeits the deduction while still reducing basis at sale.
Adjusted basis after depreciation = Initial basis + capital improvements − depreciation allowed or allowable. Example: you start with a $264,937 building basis. After 10 years at $9,634/year (simplified), you have taken $96,340 of depreciation. If you added a $15,000 roof replacement in year 4 (depreciating at $545/year over 27.5 years) and a $12,000 HVAC in year 7 (depreciating separately), your adjusted basis calculation includes the original building, the roof, the HVAC, each with their own remaining basis.
Practically, the easiest way to track this is to maintain a depreciation schedule in your tax software or with your accountant. Every asset on the schedule should have: description, date placed in service, cost, recovery period, prior year cumulative depreciation, and current year depreciation. The sum of all current-year deductions flows to Schedule E; the sum of all cumulative depreciation is what reduces your basis at sale.
A complete basis tracking example
Take a property purchased in January 2015 for $320,000, with $3,500 in basis-increasing closing costs. The county assessor's land/improvement ratio is 20% land / 80% building. Initial building basis = ($320,000 + $3,500) × 80% = $258,800.
Over 10 years (2015–2024): annual depreciation at $258,800 ÷ 27.5 = $9,411/year × 10 years = $94,109 cumulative depreciation. You replaced the HVAC in 2017 for $8,500 (depreciated as 5-year property under bonus depreciation — fully expensed in 2017, adding nothing to basis after that). You replaced the roof in 2019 for $14,000 (treated as a component of the building, depreciated over remaining 27.5-year life starting 2019 — roughly $509/year × 6 years = $3,055 depreciation on the roof, with $10,945 roof basis remaining). You repainted in 2022 for $3,500 — a deductible repair, not capitalized.
Adjusted basis calculation in 2024: Original building basis $258,800 − $94,109 (10 yrs depreciation) + $14,000 (roof added to basis) − $3,055 (roof depreciation) = $175,636. Land basis: $323,500 × 20% = $64,700. Total adjusted basis: $175,636 + $64,700 = $240,336.
If you sell the property for $480,000 with $25,000 in selling costs, your amount realized is $455,000. Taxable gain = $455,000 − $240,336 = $214,664. Of that, $97,164 ($94,109 + $3,055) is depreciation recapture taxed as unrecaptured Section 1250 gain (up to 25% federal rate). The remaining $117,500 is long-term capital gain (0%, 15%, or 20% depending on your income). Knowing this split is impossible without the detailed depreciation tracking.
Basis after a 1031 exchange
When you sell a rental and defer gain with a 1031 exchange, you do not get a fresh start on basis. Instead, the IRS gives you a carryover basis in the replacement property: start with your adjusted basis in the relinquished property, then make adjustments for any boot received or paid and any gain recognized. The formula is: replacement property basis = relinquished property adjusted basis + gain recognized + additional cash paid into the exchange − boot received.
Example: you exchange a property with $240,000 adjusted basis and $480,000 fair value (a $240,000 deferred gain) for a replacement property worth $500,000, with no boot. The replacement property's initial basis is $240,000 — exactly the same as the relinquished property's adjusted basis. The deferred gain is locked into the low basis. When you eventually sell the replacement property (without another 1031), that low basis magnifies the taxable gain. The 1031 deferred the tax, not eliminated it.
Report the exchange on IRS Form 8824 in the year of the exchange, and carry the computed basis over to Form 4562 (depreciation schedule) for the replacement property. Restart depreciation on the replacement property using the carryover basis PLUS any additional cost (if you paid any boot out-of-pocket), spread over the replacement property's remaining recovery period.
Inherited and gifted property basis
When you inherit rental property, your basis is "stepped up" (or stepped down) to the property's fair market value on the date of the decedent's death (or the alternate valuation date elected by the estate). All prior depreciation is wiped away for your purposes. You depreciate the inherited FMV over a fresh 27.5-year term starting from the date of inheritance. This is why inherited rentals are so tax-efficient: decades of accumulated gain in the decedent's hands disappear.
When you receive rental property as a gift, the rules are more complex. Your basis for computing gain is the donor's carryover basis at the time of the gift (plus any gift tax the donor paid attributable to the appreciation). Your basis for computing a loss is the lower of the donor's basis or the FMV at the time of the gift. If the property has declined in value since the donor's purchase, you may not be able to recognize the full economic loss — you get the lesser of carryover basis or FMV as your loss basis.
In both inherited and gift situations, document the basis thoroughly at the time of the transfer. For inherited property, get a date-of-death appraisal. For gifted property, obtain the donor's full depreciation history and cost basis records.
Records to keep — forever
Basis records must be kept as long as you own the property, plus at least three years after you file the return for the year of sale. The IRS can audit basis claims for up to six years if underreported income exceeds 25% of what was reported (and there is no statute of limitations for fraudulent returns). For basis — which can span decades of ownership — the practical answer is: keep everything permanently or until well after any statute of limitations could apply.
The minimum records you need: original closing disclosure or HUD-1 from purchase; county assessor's assessment showing land/building split; receipts or contracts for every capital improvement (do not discard renovation invoices); annual depreciation schedules (IRS Form 4562 or your tax software's asset detail); Form 8824 from any 1031 exchange; appraisals for any inherited or donated property.
Store originals digitally. Many title companies, lenders, and county recorders now offer document retrieval, but primary responsibility for basis documentation is yours. Losing records does not excuse you from the tax — it just means a costly reconstruction project at audit time, often with numbers that are hard to defend.
Common basis tracking mistakes to avoid
Not separating land and building at purchase. If you depreciate your entire purchase price (including land) you are overclaiming depreciation and understating basis. The IRS can disallow the land portion of depreciation on audit.
Capitalizing repairs as improvements. Ordinary repairs do not increase basis, but capitalized improvements do. If you capitalize a repair and fail to take the current deduction, you overstate basis and understate current deductions. The TPR safe harbors exist to make this distinction cleaner — use them.
Forgetting depreciation on improvements. Every capitalized improvement starts a new depreciation stream. A $15,000 roof replacement is not just a basis add — it is also a new depreciation asset generating roughly $545/year in deductions. Missing improvement depreciation understates your expense and overstates your basis, giving you the worst of both worlds.
Using purchase price as your selling basis. This is the most expensive mistake. Adjusted basis at sale equals initial basis plus improvements minus all depreciation taken or allowable over the entire holding period. Using the purchase price ignores decades of depreciation and produces a computed gain far lower than what the IRS will calculate — and the IRS's number will prevail.
Frequently asked questions
What is adjusted basis in a rental property?
Adjusted basis is your initial cost basis (purchase price plus basis-increasing closing costs) plus any capital improvements, minus all depreciation you have claimed or were allowed to claim. It is the number you subtract from your amount realized at sale to compute taxable gain.
Does depreciation reduce my tax basis even if I forgot to take it?
Yes. The IRS rule is "allowed or allowable" — basis is reduced by the depreciation you were entitled to claim whether or not you actually took it. Skipping depreciation forfeits the deduction without preserving your basis. If you missed years of depreciation, file Form 3115 to catch up in a single year.
How do I find my land vs. building allocation?
The most defensible method is the county property tax assessor's land-to-improvement ratio, which you can find on your property tax assessment notice or on the assessor's website. Apply that ratio to your cost basis to split between non-depreciable land and depreciable building.
What happens to basis in a 1031 exchange?
You carry the relinquished property's adjusted basis over to the replacement property, adjusted for any boot paid or received and any recognized gain. You do not get a fresh start on basis — the deferred gain is embedded in the replacement property's low carryover basis, and you depreciate over the replacement property's remaining life.
How long must I keep basis records?
Keep all basis documentation at least as long as you own the property plus three to six years after the tax year of sale. Because basis tracks across decades of ownership, the practical answer is to keep records permanently or scan and store them digitally.
Do capital improvements always increase basis?
Improvements you capitalize (rather than expense under a safe harbor) increase your basis. Improvements you deduct currently under the de minimis or small-taxpayer safe harbor do NOT increase basis — they reduce current taxable income instead. Choose thoughtfully, as each treatment affects both your current deductions and your eventual gain.
What is the basis of inherited rental property?
The basis of inherited rental property is stepped up (or stepped down) to the property's fair market value on the date of the decedent's death. Prior depreciation deductions taken by the decedent are irrelevant to your basis — you start fresh with the FMV and depreciate over a new 27.5-year term.
Sources
Educational information and estimates only. Not tax advice. Tax rules change and vary by situation; consult a qualified tax professional before acting.