Business Mileage & Vehicle Deductions: Standard Mileage vs. Actual Expenses

The deduction you lose by not writing it down

Using your car for business is one of the most common deductions small-business owners have — and one of the most commonly underclaimed, because the value lives or dies on a record almost nobody keeps in the moment: a contemporaneous mileage log. The deduction is real and often substantial. The catch is that the IRS expects you to be able to prove the business miles, and "I drove a lot for work" is not proof. This guide covers the two ways to deduct vehicle costs, how to keep a log that actually holds up, and how to think about which method to choose.

This is general education, not tax advice. Vehicle rules have specific definitions and the rates change yearly — confirm your situation with a tax professional.

First principle: only business miles count

Before either method, you have to separate business miles from personal miles, because only the business portion is deductible. And critically, your daily commute — driving from home to a regular workplace — is generally personal, not business. Business miles are trips like driving to a client, to a job site, to pick up supplies, or between two work locations.

This split is the foundation of everything below. Both methods deduct only the business share, so the percentage of your driving that's genuinely for business is the number you're really protecting with your records.

Method 1: the standard mileage rate

The standard mileage method multiplies your business miles by a single per-mile rate the IRS publishes each year. That one rate is meant to cover everything — gas, oil, maintenance, insurance, registration, and depreciation — bundled into a single number per mile.

• Pro: dramatically simpler. You track miles, not a stack of receipts. Drive 8,000 business miles, multiply by the year's rate, done.
• Con: if your actual costs per mile run high (an expensive vehicle, heavy repairs, low fuel economy), the flat rate can leave money on the table.
• A rule worth knowing: if you want the option to use the standard rate over a car's life, you generally have to choose it in the first year you use the vehicle for business. Lock-in rules apply, so this isn't a year-to-year coin flip — ask before you default into one method.

Because the rate changes annually, always use the current year's figure rather than last year's.

Method 2: actual expenses

The actual-expense method adds up what the vehicle really cost you for the year — fuel, maintenance and repairs, insurance, registration, lease payments or depreciation if you own it — and deducts the business-use percentage of that total.

That business-use percentage comes straight from your mileage log: business miles ÷ total miles. If you drove 20,000 miles total and 12,000 were for business, your business-use percentage is 60%, and you deduct 60% of every eligible vehicle cost.

• Pro: for expensive vehicles or high real costs, this often deducts more.
• Con: far more recordkeeping — you're keeping receipts and tracking depreciation, which works like depreciating any other asset.

Notice that both methods still require the mileage log. Even actual expenses need the business-use percentage, and that percentage comes from miles. There is no version of this deduction where you get to skip tracking miles.

The mileage log that actually holds up

This is the part that determines whether your deduction survives scrutiny. A defensible log records, for each business trip:

• The date.
• The destination and business purpose — "Acme Co., client meeting," not just "work."
• The miles driven.

The magic word is contemporaneous — kept at or near the time of the trip, not reconstructed from memory in April. You also want your odometer reading at the start and end of the year, so your total annual mileage is documented and the business-vs-total split is grounded in real numbers. A reconstructed, estimated log is exactly what gets deductions thrown out; a steady, boring, real-time log is what makes them routine.

Which method should you pick?

There's no universal answer, but some reliable instincts:

• Lean standard mileage when you drive a lot of business miles in a reasonably economical car and value simplicity. The flat rate is generous relative to a cheap-to-run vehicle, and the recordkeeping is light.
• Lean actual expenses when the vehicle is expensive to own or operate — high depreciation, costly insurance, frequent repairs — so your real per-mile cost beats the flat rate.
• Remember the first-year choice. Because choosing the standard rate in year one preserves flexibility later, the safe default for many owners is to keep both a mileage log and basic expense receipts in the first year, then let the math (and your accountant) pick.

Book it like any other expense

Whatever you choose, the bookkeeping is the same discipline as the rest of your records:

• Give vehicle costs their own categories in your chart of accounts so actual-expense totals are a report, not a search.
• Keep the log and receipts with your other audit-ready records.
• Reconcile monthly so fuel and repair charges tie to your bank, the same habit behind bank reconciliation.

The deduction is yours for the taking — it just asks for a small, steady habit in return. Keep the log honestly and in the moment, pick the method that fits your vehicle, and the miles you already drive turn into money you don't leave behind. Hosting Books keeps your vehicle expenses categorized and reconciled alongside everything else, so when it's time to compare the two methods the actual-cost side of the math is already done.

This article is general information, not tax advice. Vehicle deduction rules and the standard mileage rate change yearly and depend on your facts — confirm with a qualified tax professional.