Splitting Business vs Personal Expenses
Mixing personal and business expenses distorts your financial statements and inflates (or hides) your real tax liability. Here's how to split them correctly.
For each expense, apply a business-use percentage: deductible amount = total amount × (business-use % ÷ 100). Fully business expenses use 100%, fully personal use 0%.
Common mixed-use expenses
Phone and internet bills, home-office utilities, and a personal vehicle used partly for business are the most common mixed-use cases — each typically gets a business-use percentage reflecting actual usage, rather than a flat 0% or 100%.
Keep evidence for the percentage you use
A simple log or reasonable, documented estimate of actual usage (e.g. call logs, mileage records) supports your business-use percentage if it's ever questioned — round numbers with no basis are the most common audit flag.
Try Free Web Tools Mentioned in This Guide
Business vs Personal Expense Splitter
Split mixed expenses into deductible business and non-deductible personal amounts.
Quarterly Tax Calculator
Estimate US self-employment quarterly tax payments so you're never caught by surprise.
Tax Set-Aside Calculator
Log each payment and instantly see how much to move to savings for taxes.
Frequently Asked Questions
What happens if I don't split mixed expenses?↓
Claiming 100% of a mixed-use expense as a business deduction overstates deductions (raising audit risk), while claiming 0% understates them (overpaying tax) — neither reflects reality.
Does this file taxes for me?↓
No — this only splits and totals expenses so you (or your accountant) know what's deductible. It doesn't file or submit anything.