One thing I see all the time during tax season is clients trying to deduct the business use of their car, but they are going about it the wrong way. Someone will say: “Here’s a $700 repair for my car.” Another person sends over a spreadsheet that only lists gas. Then, when I start explaining how vehicle deductions actually work, that’s when the frustration begins.
The reality is that you usually can’t deduct the full cost of those expenses. The IRS requires us to determine how much of the vehicle’s use was for business, and that calculation starts with mileage. Without that information, a few random expenses by themselves don’t tell the full story of how the car was actually used for business.
As an Enrolled Agent, my job isn’t to block deductions. My job is to make sure that the deductions you take are calculated correctly and can be supported if the IRS ever asks questions. When the information needed to support the deduction isn’t there, I can’t file a complete and accurate return.
There’s a right way to handle vehicle deductions that allows you to claim what you’re entitled to while keeping the IRS off your back. And then there’s the lazy, half-done way that can eventually lead to a very expensive letter showing up in your mailbox.
Today, I’m going to walk through the right way to do it.
The Two Ways to Deduct Business Use of a Car
The IRS allows you, as a business owner or self-employed professional, to deduct expenses incurred for using your car for business purposes. This includes driving to client meetings, making deliveries, or running errands for supplies. There are two deduction methods you can choose from:
- Method 1: The Standard Mileage Method
- Method 2: The Actual Expense Method
Both methods require recordkeeping, but one is much simpler than the other. And you cannot “double dip” by using both methods.
Method 1: The Standard Mileage Method (The Simple Choice)
The standard mileage method is the path of least resistance. It’s the one I recommend for the majority of my clients. With this method, you don’t care how much gas costs in July. You don’t care about the price of tires. Instead, you multiply your total business miles by a set rate determined by the IRS.
For 2026, the IRS has set the mileage rate at 72.5 cents per mile.
Let’s look at a real scenario. If you drove 5,000 miles for your business this year:
5,000 miles × $0.725 = $3,625 deduction.
That’s it. Nothing more, nothing less. Pretty straightforward.
But here’s the part that everyone gets wrong: You cannot just “guess” that you drove 5,000 miles. “About 100 miles a week” is not a legal tax record. The IRS requires a contemporaneous log. That’s a fancy way of saying you need to record the miles as they happen, not 14 months later when you’re sitting at your kitchen table trying to remember where you went last February.
The log needs to include:
- The date of the trip
- The starting point and the destination
- The business purpose (e.g., “Meeting with New Client”)
- The odometer readings or total miles driven
If you don’t track the miles, the deduction doesn’t exist. It’s that simple.
When You Can Use the Standard Mileage Method
To use the mileage method, you must own or lease the vehicle, and there are a few situations where it can’t be used. For example, the mileage method cannot be used if you:
- Operate five or more vehicles at the same time (like a fleet)
- Claimed a Section 179 deduction on the vehicle in the past
- Claimed bonus depreciation on the car
- Used accelerated depreciation methods
Because of these rules, the decision you make in the first year matters more than most people realize.
Personally, I advise my clients that if they own their vehicle, they should choose the mileage method in the very first year the car is used for business. If you don’t use it the first year, you are forever locked out of using it for that specific vehicle.
If the vehicle is leased, you must continue using whichever method you start with for the entire lease period.
Method 2: The Actual Expense Method
The second option for deducting your business use of your car is the actual expense method. This is exactly what it sounds like: you deduct the real-world costs of keeping that car on the road. This includes:
- Gas
- Oil changes
- Repairs
- Tires
- Insurance
- Registration fees
- License fees
- Lease payments
- Depreciation
If you use this method, you must track these expenses throughout the year and keep the receipts to support the amounts being claimed.
This sounds great on paper until you realize the IRS requirement for the Business Use Percentage. The business use percentage only allows you to deduct the portion of vehicle expenses that matches your business miles for the year. You cannot deduct 100% of your gas bill unless that car never goes to the grocery store, never picks up the kids from school, and never drives to a friend’s house. And most people use their cars for both.
To find your deduction, you take:
(Business Miles ÷ Total Miles Driven) = Business Use %
If you drove 12,000 miles total this year, but only 4,000 were for business, your business use is 33%. You then take all those receipts you’ve been saving and multiply the total by 33%.
If you spent $6,000 on your car for the year, your deduction is only $1,980.
Compare that to the Standard Mileage Method for those same 4,000 miles:
4,000 x $0.725 = $2,900.
In this scenario, the “simple” method actually gave you a larger deduction. This is why guessing doesn’t work. You need to see the numbers.
The Bonus: Parking and Tolls
Here is a small win: no matter which method you choose, you can still deduct 100% of your business-related parking fees and tolls.
These are considered “out-of-pocket” business expenses. They aren’t wrapped into the 72.5 cent mileage rate, and they aren’t subject to the business use percentage. If you paid $20 to park at a convention, that’s a $20 deduction. Just make sure you keep the receipts..
This is Where People Get Burned
No matter which method you use, everything comes back to one thing — your mileage log. That mileage log is what shows how much of your driving was actually for business.
If you are audited and you cannot produce a mileage log, the IRS doesn’t just “trim” your deduction. They remove it. Entirely.
So what happens?
- The deduction is reversed.
- Your taxable income goes up.
- You owe the back taxes.
- Penalties are added for “underpayment.”
- Interest is charged, calculated all the way back to the original due date.
And all of that stress is completely unnecessary. All it takes is a simple app on your phone or a $5 notebook in your glove box.
The Bottom Line
If you qualify for a vehicle deduction, you should absolutely take it. It’s one of the most common ways self-employed individuals lower their tax liability. But it needs to be done with integrity and proper documentation.
Keeping a clean mileage log isn’t just about taxes — it’s about running your business with good records. When the records are clean, the deduction is easy to support. And when the deduction is easy to support, tax season becomes much less stressful.
You don’t have to figure all of this out on your own. Whether you’re trying to catch up on old returns or want to make sure your 2026 tax strategy is on the right track, I can help you put the right systems in place.
When you’re ready to get your taxes back on track, I’m here to help.
