If you drive for your business — to client sites, job sites, the bank, the supply store — those miles are a real deduction. For many service businesses and contractors, they add up to thousands of dollars a year. They are also one of the first things to fall apart when the records are thin, because a mileage deduction is only as good as the log behind it.
The problem is rarely that owners do not drive enough to matter. It is that they plan to "figure it out at tax time," and by then the calendar is fuzzy, the receipts are gone, and the number that ends up on the return is an estimate nobody can back up. October is a good moment to fix that: there is still a full quarter left to record cleanly and enough time to rebuild the first nine months while your calendar and invoices are still fresh.
What a mileage log needs to show
A usable log is not complicated, but it does need to be specific. For each business trip, record:
- The date of the trip.
- Where you went — the destination or client, not just "errands."
- The business purpose — "site visit, Miller kitchen remodel" holds up far better than "work."
- The miles driven, either from odometer readings or a reliable app or map calculation.
Also note your total miles for the year on each vehicle — a January 1 and December 31 odometer reading is enough. Business use is measured against total use, so without the total, the business miles have nothing to be a percentage of.
The key word is contemporaneous. A log kept at or near the time of the trip carries much more weight than one reconstructed months later from memory. Reconstruction from solid evidence is better than nothing, but it is the weakest version of the record.
Know which miles count
Not every drive in a work vehicle is a business mile. As a general rule:
- Commuting does not count. Driving from home to your regular place of business is personal, even if you take calls on the way.
- Trips between work locations usually do. Office to client, job site to supplier, one client to the next.
- A home office can change the picture. If your home is your principal place of business, trips from home to clients may qualify — but the rules are specific, so do not assume.
- Personal stops break the trip. A detour to pick up groceries on the way back from a client is not business mileage for that leg.
Standard rate or actual expenses
There are two ways to turn miles into a deduction. The standard mileage rate multiplies your business miles by a per-mile rate the IRS sets each year — simple, and it only requires the log. The actual expense method takes your real costs — fuel, insurance, repairs, depreciation, registration — and deducts the business-use percentage of them. That requires the log and every vehicle receipt.
Which one comes out ahead depends on the vehicle, how much you drive, and how the vehicle is owned, and the choice you make in the first year can limit your options later. This is exactly the kind of decision to confirm with your CPA before you file. Either way, the mileage log is the foundation; without it, neither method holds up.
Not sure your vehicle records would survive a question from the IRS? We will review your mileage and vehicle expenses as part of a free 30-minute books check.
A real-world example
A residential electrician drove his truck to three or four jobs a day but had never kept a log. Each spring his tax preparer asked for a mileage number, and each spring he gave a round guess — and then trimmed it down because he was nervous about claiming something he could not prove.
When we cleaned up his books, we matched his invoices and job calendar against map distances from his shop to rebuild the year, then set him up with a phone app that recorded trips automatically and let him tag each one as business or personal with a swipe. His first full year with a real log showed nearly twice the business mileage he had been claiming. Just as important, he had a record he could hand over without worrying about it.
Catching up before December 31
If you have not been tracking this year, do not wait until next year to start. Two steps, in this order:
- Start a real log today. An automatic tracking app is the easiest option; a notebook in the glove box works if you will actually use it. Record your current odometer reading now.
- Rebuild January through September from evidence. Use your calendar, invoices, client addresses, and fuel receipts to reconstruct trips, and keep a note of what sources you used. Be conservative — a smaller number you can support beats a larger one you cannot.
While you are at it, keep fuel, repair, and insurance receipts with the rest of your records. Our guide to lost receipts and lost deductions covers a simple way to capture them. If the vehicle is also used personally, keep its costs clearly separated — the same principle we cover in why mixing personal and business money costs more than you think. And add the mileage log to your Q4 bookkeeping checklist so it is closed out with everything else.
Rules on vehicle deductions, home-office trips, and the yearly standard rate change and depend on your situation, so confirm the specifics with your CPA before you file.
How Shieldbearer Ledger Co. helps
We make vehicle records part of your regular monthly bookkeeping instead of a scramble at tax time. We help you pick a tracking method that fits how you work, categorize fuel, repairs, and insurance correctly, keep business and personal vehicle costs separate, and hand your CPA a clean year-end mileage summary with the log behind it. You claim what you have earned — and you can prove it.