How to Calculate Cost Basis for a Rental Property

The cost basis of a rental property is the starting point for every tax calculation that follows—from depreciation deductions to capital gains when you sell. It includes far more than the purchase price alone: settlement fees, improvements, and crucially, the depreciation you’ve already claimed come into play.

What Enters Your Initial Cost Basis

The foundation of your rental property’s cost basis is the purchase price you paid—but it does not stop there. The IRS requires you to include all amounts you paid to acquire the property and make it ready for rental use.

Acquisition costs bundled into basis typically include:

• Earnest money and down payment
• Purchase price of the building and land
• Closing costs: title search, title insurance, recording fees, deed recording
• Loan origination fees and points paid to secure financing
• Attorney fees and title transfer taxes
• Property inspection fees paid to verify condition before purchase
• Appraisal costs
• Any real estate commissions you paid (usually the seller bears these, but if you pay, it counts)

These go into your opening basis. They are not deducted in the year of purchase; instead, they become part of the depreciable basis of the building (not the land—land does not depreciate).

Separating Building from Land

Cost basis splits into two components: the building and the land. Only the building is depreciable. On the form-8949 you eventually file to report the sale, you must track these separately, because land basis carries forward unchanged; building basis is reduced by depreciation claimed.

When you purchase a property, if the purchase contract and closing statement do not separately list a value for the building and land, you must allocate the purchase price between them. The most reliable method is the assessed value ratio: take the property tax assessor’s values for the land and building, divide the building value by the total, and apply that ratio to your purchase price. This becomes your opening building basis.

For example: You pay $400,000 for a rental home. The property tax assessment shows a land value of $100,000 and building value of $300,000 (total $400,000). The building represents 75% of assessed value. Your building basis is $400,000 × 0.75 = $300,000. Land basis is $100,000.

Capital Improvements vs. Repairs

Not every expense that improves the property adds to cost basis. The distinction between a capital improvement and a repair is critical.

A capital improvement adds to basis when it:

• Extends the useful life of the property
• Adds permanent value to the building (e.g., a new roof, HVAC system, addition, new windows, flooring)
• Adapts the property to a new or different use (e.g., converting a single-family house into a duplex)

A repair does not add to basis when it:

• Maintains the property in its existing condition (e.g., patching the roof, painting walls, fixing plumbing)
• Restores the property to its pre-damage condition after damage or wear
• Does not appreciably extend the building’s life

When in doubt, the safe approach: if the cost is large and the work lasts many years, capitalize it and add it to basis. If it is routine maintenance, deduct it as a current repair expense in that year.

Example: Replacing a broken toilet (repair, deductible immediately). Installing a brand new HVAC system (capital improvement, added to basis and depreciated over 27.5 years).

Calculating Adjusted Basis

After you own the property, your basis changes every year you claim depreciation because the IRS requires you to reduce basis by the depreciation you take—whether or not you actually claimed it on a tax return.

Adjusted basis = Initial basis + Capital improvements − Depreciation claimed (and required)

Once you rent a residential building to tenants, you may claim depreciation. The annual depreciation is calculated as:

Annual depreciation = Building basis ÷ 27.5 years = Building basis × 3.636%

Over 27.5 years, you will depreciate away 100% of the building’s cost (not the land).

Example: You have a building basis of $300,000. In year one, depreciation is $300,000 ÷ 27.5 = $10,909. Your adjusted basis at the end of year one becomes $300,000 − $10,909 = $289,091. In year two, you again claim $10,909 depreciation (same amount every year if straight-line), and adjusted basis drops to $278,182. This pattern repeats for 27.5 years.

If you skip claiming depreciation in any year, you are still required to reduce basis by the depreciation you could have claimed. The IRS will assess depreciation-recapture-investor tax on the full amount if you sell.

Adjustments at Purchase or After

Several events trigger basis adjustments after acquisition:

• Capital improvements: Add to basis, then depreciate over their own useful life (or the remaining life of the building, whichever is shorter).
• Tenant improvements: If you pay to improve the unit for a tenant, capitalize them and depreciate.
• Casualty losses and insurance recovery: If the building is damaged and you receive insurance proceeds less than the damage, you may deduct the loss; if proceeds exceed damage, basis increases.
• Cost segregation: A cost-segregation study allocates portions of basis to shorter-lived assets (5–15 years) instead of 27.5 years, accelerating write-offs. This is optional but can substantially increase early deductions.

When you refinance the mortgage, the loan amount does not change basis. Basis only changes when you spend additional cash improving the property.

Reconciling Basis Before a Sale

When you eventually sell the property, you need to know your adjusted basis with precision. Gather:

1. The original settlement statement showing all acquisition costs
2. Records of every capital improvement and its cost
3. A schedule showing annual depreciation claimed for every year of ownership
4. Any insurance recoveries, casualty loss deductions, or basis adjustments

On form-8949, you will report:

• Cost basis = Adjusted basis at the time of sale
• Amount realized = Sale price − selling costs (real estate commission, closing costs)
• Realized gain = Amount realized − Cost basis

If your adjusted basis is wrong, your capital gains tax will be wrong. Keeping accurate records from the day you acquire the property is the only insurance against audit or overpayment.

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