Claiming a mileage deduction can put real money back in your pocket, but only if you can prove it. The IRS doesn't take your word for how far you drove for work — it expects documentation that holds up under scrutiny. If you're audited without solid records, even legitimate business miles can be disallowed. Knowing exactly what to keep, and how to keep it, is the difference between a deduction that sticks and one that vanishes.
Why Records Matter More Than the Method
There are two ways to deduct vehicle costs for business: the standard mileage rate and the actual expense method. The standard mileage rate multiplies your business miles by a set per-mile figure that the IRS updates each year. The actual expense method tallies up what you really spent — gas, oil, repairs, insurance, depreciation, and more — then applies the percentage of driving that was business-related.
Whichever you choose, both approaches share one non-negotiable requirement: you have to substantiate your business use. The standard method still demands a reliable count of business miles. The actual method demands that plus receipts for every cost you claim. In other words, no method lets you skip the recordkeeping — it only changes what you're recording.
The Mileage Log: Your Core Document
The heart of any mileage deduction is a contemporaneous log — a record kept at or near the time of each trip, not reconstructed from memory months later. For each business drive, your log should capture:
- The date of the trip
- The starting point and destination, or where you went
- The number of miles driven for that trip
- The business purpose — why the trip was necessary for your work
- Whom you met with, when the trip involved a client, customer, or business contact
That last detail matters more than people expect. A log entry that simply says "25 miles" tells an auditor nothing. An entry that reads "March 12, office to client site at 400 Main St, met with J. Rivera to review contract, 25 miles" paints a complete, defensible picture. The purpose and the person are what transform a number into evidence.
Contemporaneous Beats Reconstructed
The IRS gives far more weight to records created as events happen. A log you build in real time — even a quick note after each drive — carries credibility that a spreadsheet cobbled together at tax time simply can't match. If you drive for rideshare, deliveries, or client visits, building the habit of logging immediately protects you long before you ever file.
Total Miles, Not Just Business Miles
One point trips up many first-time filers: you can't just track your business trips. To calculate the business-use percentage of your vehicle — which you need for the actual expense method and which supports your overall claim — you have to know your total annual mileage too.
The simplest way is to record your odometer reading at the start of the year and again at the end. The difference is your total miles. Your business miles, drawn from your log, then become a clean fraction of that total. Recording odometer readings at the beginning and end of each business trip, or at least noting them periodically, strengthens the trail even further.
Receipts and Supporting Documents
If you use the actual expense method, your mileage log is only half the story. You also need to keep every receipt tied to operating and maintaining your vehicle, including:
- Gas and oil purchases
- Repairs and routine maintenance
- Tires
- Insurance premiums
- Registration fees and licenses
- Lease payments or documentation supporting depreciation
- Parking fees and tolls incurred for business
Parking and tolls deserve a special note: they're deductible for business trips even if you use the standard mileage rate. So keep those receipts regardless of which method you pick. Because the actual expense method leans on detailed, itemized proof, its recordkeeping burden is heavier — every dollar you claim needs a document behind it.
How Long to Keep Everything
Records aren't something you toss once you've filed. The IRS can examine returns for several years after filing, so hold on to your mileage logs, receipts, and odometer records for at least three years from the date you file — and longer is safer if you have the space. Storing them digitally, backed up in more than one place, means a lost shoebox never costs you a deduction.
Making Recordkeeping Sustainable
The reason people lose deductions is rarely that they didn't drive the miles — it's that keeping a handwritten log every single day is tedious and easy to forget. The fix is to make the process as automatic as possible. Many drivers now rely on apps that record trips using GPS and let you tag each one as business or personal with a tap; Rienly, for instance, tracks your mileage while also keeping your vehicle's maintenance schedule in one place, which happens to line up neatly with the repair and service receipts the actual expense method requires.
Whatever tool you use, aim for a system that captures the date, distance, destination, and purpose without requiring you to remember details later. The best record is the one you actually keep.
A Simple Checklist Before You File
- A trip-by-trip mileage log with date, miles, destination, purpose, and business contacts
- Your total annual mileage, ideally from start- and end-of-year odometer readings
- Receipts for parking and tolls from business trips, no matter which method you use
- Full vehicle expense receipts if you're using the actual expense method
- Backup copies stored safely and kept for at least three years
The Bottom Line
A mileage deduction is one of the most valuable write-offs available to people who drive for work — but it lives and dies by your records. The standard mileage rate simplifies the math, yet it still requires a credible, contemporaneous log. The actual expense method can yield a bigger deduction but demands receipts for everything. In both cases, the drivers who come out ahead are the ones who log trips as they happen, note the who and why behind each drive, and hold on to their documentation. Build that habit now, and when tax season — or an audit — arrives, your deduction will be ready to defend itself.