What each trip entry should show
The usual elements are the date, the starting point, the destination, the business purpose, and the miles driven. The odometer readings at the start and end of the year let you total all miles and compute the business share. Missing the purpose is the most common weakness, so write it every time.
Be specific. Client meeting with the Rivera account is better than business. A bank deposit trip should say deposit. Enough detail that you could explain it two years later.
Pick a capture method
A paper notebook in the glove box works if you are disciplined. A spreadsheet works if you update it weekly. Phone apps can track trips by GPS and let you classify each as business or personal with a swipe. The right method is the one you will actually use.
Whichever you choose, record on the day of the trip or very close to it. Records made at the time are more credible than ones recreated later.
Commuting and what is not business
Travel between home and a regular workplace is generally treated as commuting, not business mileage. There are exceptions, for example when you have a home office that is your principal place of business. Ask your preparer how the rules apply to your situation.
Keep personal trips out of the log, but do count them in your total yearly miles. The business percentage is business miles divided by all miles.
Year-end tasks
At year end, photograph the odometer on the last day. Total the log, check for gaps such as weeks with no entries during busy periods, and compare to your calendar. A log that shows no trips in a month when you saw clients all month will raise questions.
Hand your preparer the log totals, the odometer photos and the vehicle's first date of business use. They choose the calculation method with you.
Do not rely on a remembered rate
The mileage rate set by the IRS is updated regularly. Ask the preparer or check the IRS site for the correct figure for your tax year. Your log should record miles only, and the dollar figure is computed later.
Parking and tolls for business trips are tracked separately from mileage. Record them in your books with receipts.
A short example of a good entry
A strong entry reads like this: March 9, from the office to a client site for an installation estimate, then to the supply house for parts, then back to the office, with start and end odometer readings and the total for the day. Compare it to an entry that only says driving, which proves almost nothing.
Round trips with several stops can be logged as one entry if the purposes are listed. What matters is that each stop and reason is visible and the totals add up.
Worked example with numbers
A good entry: March 14, 2026, start 41,820, end 41,861, 41 miles, from the office to the client site in Edison and back, meeting about a bookkeeping engagement. Add up the year to find business miles, then divide by total miles for business use. Look up the current IRS standard rate before calculating.
Mistakes that cost money
Rebuilding the log at year end. Missing the purpose. Counting commuting. Using a remembered rate.
Check your work
Each month, check that the odometer readings are continuous.
Common questions
Can I estimate my mileage with maps?
Mapped distances can supplement a log, but the record should still show date, destination and purpose, and be made close to the time of the trip.
Do I need a log if I use the actual expense method?
You still need to show the business-use share, so a log of business and total miles remains important.
What if I forgot to log for months?
Reconstruct from calendar, invoices and emails as accurately as possible, label it as reconstructed, and start logging now.
This guide is general information, not tax, legal or accounting advice. Rules, fees and due dates change; check with the IRS, the NJ Division of Taxation or a licensed professional for your situation.