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Are you using the right method for your deductions?

Home office and vehicle are the two deductions most commonly taken wrong — wrong method, wrong amount, or not taken at all. Enter your numbers and see both IRS methods side by side. If you’re a sole prop, you’ll also see the self-employment tax savings most owners don’t realize they’re leaving on the table.

2025 IRS rates · Educational estimate · Not tax advice

Your situation

Annual net income120,000

Net self-employment income (sole prop) or total income (S-corp).

30,000600,000
Filing status
Business structure

Home office

Dedicated office space200 sq ft

Used regularly and exclusively for business

0 sq ft1,000 sq ft
sq ft
Total home size1,200 sq ft
200 sq ft6,000 sq ft
sq ft
Monthly home expenses$2,500

Rent or mortgage interest + utilities + insurance

$500$15,000
$

Vehicle

Business miles this year8,000 mi

Client visits, meetings, errands — commuting doesn't count

0 mi60,000 mi
mi
Total miles this year15,000 mi
1,000 mi100,000 mi
mi
Your total vehicle costs$8,000

Gas, insurance, maintenance, registration, lease or depreciation

$0$40,000
$

Estimated deductions

Total deduction

$10,600

Estimated tax savings

$3,862

Income tax savings

$2,364

SE tax savings

$1,498

Marginal income tax rate24.0%
Effective savings rate on deductions36.4%

Home office

Simplified method

$1,000

$5 × 200 sq ft

Regular method

Use this

$5,000

16.7% of annual home expenses

The regular method saves you $4,000 more at your numbers. The tradeoff: you need to track actual expenses and file Form 8829.

Vehicle

Standard mileage

Use this

$5,600

8,000 mi × $0.70

Actual expenses

$4,267

53.3% of $8,000

Method lock-in:You must choose a method in the first year you place the vehicle in service. If you start with actual expenses, you generally can’t switch to standard mileage for that vehicle. The $0.70/mile rate is the 2025 IRS rate; the 2026 rate had not been published as of this tool’s last update.

The SE tax advantage sole props miss

Schedule C deductions reduce your net self-employment income — which lowers both your income tax and your self-employment tax (15.3%). Your 24.0% marginal rate only tells half the story. Every $1,000 you deduct also saves you approximately $141 in SE tax on top of the income tax savings. That’s why your effective savings rate is 36.4%, not just 24.0%.

Record-keeping requirements

Home office

  • Floor plan or measurements showing the dedicated space
  • Receipts for all home expenses used in the calculation
  • Form 8829 (regular method) or Schedule C line 30 (simplified)

Vehicle

  • Contemporaneous mileage log: date, destination, business purpose, miles
  • Annual odometer readings (start and end of year)
  • Receipts for all vehicle costs if using actual expense method

Educational estimate only. Home office calculations use simplified assumptions: monthly expenses entered are treated as fully deductible home costs pro-rated by square footage. The simplified method cap is $1,500 (300 sq ft × $5). Vehicle mileage rate shown is the 2025 IRS rate ($0.70/mile); the 2026 rate had not been published as of this tool’s last update. Does not model depreciation recapture, §179 or bonus depreciation for vehicles, luxury auto limits, the home office income limitation rule (deduction cannot exceed business income), or California conformity differences. SE tax savings calculation uses a simplified factor. S-corp accountable plan reimbursements require a written plan, substantiation, and compliance with employee expense rules. Results are illustrative only — not tax, legal, or investment advice. Consult a CPA before acting on any deduction strategy.

Tax data sources
  1. IRC §280A — Home office deduction rules
  2. IRC §179 — Section 179 expensing
  3. IRC §280F — Luxury automobile limits
  4. IRS Pub. 587 — Business Use of Your Home
  5. IRS Pub. 463 — Travel, Gift, and Car Expenses

Also read

Tax deductions

The Home Office Deduction: Who Qualifies, How to Calculate It, and Which Method Saves More

Self-employed business owners can deduct the business-use portion of their home — but only if it meets the exclusive-use test. Simplified vs actual method, S-corp Accountable Plan, and what the IRS looks for.

Read Tax deductions

Vehicle and Auto Deductions: Standard Mileage vs Actual Expense

Two methods to deduct business vehicle use — standard mileage (70¢/mile in 2025) or actual expense. How to choose, what documentation is required, and the luxury car and SUV limits that change the math.

Read Tax planning

Self-Employment Tax Explained: Rates, Calculation, and How to Reduce It

Self-employment tax is 15.3% on net profit — on top of income tax. How SE tax is calculated, what the deductible half actually saves, and the three ways to reduce it.

Read

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Tax services provided through Matt Reese, CPA. This page is educational and does not constitute tax or investment advice.