Mixed-Use Property Deductions: How to Deduct Expenses When a Property Is Part Business, Part Personal

By Yarik Yarosh, CPA ·September 5, 2026 ·4 min read

Written by Yarik Yarosh, CPA (US & Canada) September 5, 2026 · FL CPA license AC61704 · CPA Ontario

Most small business owners use at least some property for both business and personal purposes: their vehicle, phone, computer, home, or internet connection. The tax treatment is straightforward in principle (deduct the business-use percentage) but complex in practice because certain categories of mixed-use property (“listed property” under IRC 280F) have heightened documentation requirements, and the consequences of inadequate records are severe.

✓Key takeaway

Mixed-use property rules:

General rule: when property is used for both business and personal purposes, only the business-use portion of expenses is deductible. The business-use percentage is typically calculated as: business use hours or miles / total use hours or miles.

Listed property (IRC 280F(d)(4)):

Vehicles (passenger automobiles, including SUVs, trucks, and vans used for personal purposes)
Computers and peripherals (if not used exclusively at a regular business establishment)
Cell phones (removed from listed property by the Small Business Jobs Act of 2010, but still subject to general mixed-use rules)
Entertainment, recreation, and amusement property

Listed property special rules:

If business use is 50% or less: Section 179 and bonus depreciation aren’t allowed. Must use straight-line depreciation over ADS recovery period (5 years for autos, extended periods for other property).
If business use drops below 50% in any subsequent year: recapture the excess depreciation previously claimed (the difference between accelerated and straight-line)
Substantiation: IRC 274(d) requires contemporaneous records (log, diary, or similar) documenting business use. No record = no deduction.

Vehicle-specific rules:

Standard mileage rate: multiply business miles by the IRS rate ($0.70/mile in 2025). No other vehicle expenses deductible (except parking and tolls for business trips).
Actual expense method: total vehicle costs (gas, insurance, repairs, depreciation) x business-use percentage. Requires tracking total miles and business miles.
Cannot switch from actual to standard after the first year if MACRS depreciation was claimed.
The GVWR 6,000 lb rule: vehicles over 6,000 lbs GVWR aren’t subject to the luxury auto depreciation caps (can take full Section 179), but still must meet the 50% business use threshold.

Home (IRC 280A):

Regular and exclusive use required (higher standard than general mixed-use)
The business-use percentage applies to mortgage interest, property taxes, insurance, utilities, repairs
Personal use of the rest of the home isn’t affected

Phone and internet:

Cell phones: estimate business-use percentage reasonably; no contemporaneous log required (no longer listed property)
Internet: if the home internet is used for business, deduct the estimated business-use percentage
A dedicated business phone line or internet connection: 100% deductible (no allocation needed)

What does proper vehicle documentation look like?

Hypothetical example

Round numbers. A business owner uses their personal vehicle for both business and personal driving. Total miles for the year: 20,000. Business miles: 12,000.

Business-use percentage: 60%

Standard mileage method:

Deduction: 12,000 x $0.70 = $8,400
Documentation required: a mileage log showing date, destination, business purpose, and miles for each trip

Actual expense method:

Total vehicle costs: gas $3,000, insurance $1,800, repairs $1,200, car wash $200, depreciation $4,000 = $10,200
Business deduction: $10,200 x 60% = $6,120
In this case, standard mileage ($8,400) produces a larger deduction

Documentation required for either method:

A contemporaneous mileage log (paper or app like MileIQ, Everlance, or TripLog) recording:
- Date of each trip
- Starting and ending odometer reading (or trip miles)
- Destination and business purpose
- Business vs personal designation
Beginning-of-year and end-of-year odometer readings
Receipts for actual expenses (if using actual method)

What happens without a log:

An IRS examiner asks to see the mileage log
The taxpayer has no log
The entire vehicle deduction is disallowed ($8,400 added back to income)
Tax increase: $8,400 x 24% = $2,016 plus SE tax impact of approximately $1,285
Accuracy-related penalty (20%): approximately $660
Total cost of no log: approximately $3,961

The mileage log takes approximately 30 seconds per trip to maintain (or runs automatically with a GPS-based app). The cost of not keeping one is $3,961 in a single audit year.

Illustrative numbers only, not a real client and not advice for your facts.

Related guides:

Section 1031 Like-Kind Exchange for Small Business Real Estate

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Cite this page

Yarik Yarosh, CPA. "Mixed-Use Property Deductions: How to Deduct Expenses When a Property Is Part Business, Part Personal." Blue Cloud CPA, September 5, 2026. https://bluecloudcpa.com/guides/small-business-mixed-use-property-deductions

This guide is general information, not tax advice for your specific situation. Which points apply, and how, depends on your facts.