Capital Improvements and 1031 Exchanges: What Counts as Basis?

Why basis matters for your exchange

Your adjusted basis is the foundation of every tax calculation in a 1031 exchange. The formula:

Gain = Amount realized (sale price minus selling costs) - Adjusted basis

A higher basis means a smaller gain, which means less tax to defer (or pay, if the exchange fails). Every legitimate capital improvement you've made adds to your basis.

Investors who don't track improvements often have a lower basis than they should, resulting in an artificially inflated gain. On a property held for 15+ years, forgotten improvements can add up to $30,000-$80,000 in basis - which translates to $10,000-$30,000 in unnecessary tax exposure.

Capital improvement vs. repair

The IRS draws a line between improvements (capitalized to basis) and repairs (deducted as current expenses). The test comes from the tangible property regulations (IRC Section 263(a)):

Capital improvement - adds to basis:

• Betterment: Makes the property materially better than its original condition
• Restoration: Restores a worn component to like-new condition or rebuilds after casualty
• Adaptation: Adapts property to a new or different use

Repair - current deduction:

• Maintains property in current operating condition
• Fixes something that's broken without materially upgrading it
• Is routine and recurring in nature

The distinction sometimes feels subjective because it is. Replacing a few broken shingles is a repair. Replacing the entire roof is an improvement. Patching drywall is a repair. Gutting and rebuilding a bathroom is an improvement.

Common improvements and their classification

How improvements affect exchange math

Example: You bought a rental for $350,000 and held it for 12 years. During ownership, you replaced the roof ($18,000), remodeled both bathrooms ($22,000), and installed a new HVAC system ($12,000). That's $52,000 in capital improvements.

The investor who tracked improvements defers $10,000 less in tax - but more importantly, has accurate records that withstand audit scrutiny. The investor who didn't track improvements either overreports gain or has to reconstruct records under pressure.

Documentation requirements

Keep records of every improvement:

• Receipts and invoices. The contractor's invoice showing the work performed, date, and amount paid.
• Canceled checks or bank statements. Proof of payment.
• Before and after photos. Visual evidence of the improvement's scope.
• Permits. Building permits document the nature and timing of work.
• Your own records. A simple spreadsheet listing each improvement with date, description, cost, and contractor.

If you've lost records for older improvements, reconstruct what you can. Bank and credit card statements from the relevant years may show payments to contractors. County permit records are public. Contractors may have records going back years.

Improvements on replacement property

When you acquire a replacement property through a 1031 exchange and later make improvements, those improvements start their own depreciation schedule based on when you place them in service - not the date of the exchange. They're treated as new assets with fresh depreciation clocks.

This is separate from the carryover basis calculation on the building itself. Your CPA should track the exchange carryover basis and any post-acquisition improvements as separate depreciation schedules.

For improvement (build-to-suit) 1031 exchanges where you use exchange funds to improve the replacement property, the rules are more complex and require specific structuring through an EAT. See our improvement exchange guide for details.