What a mileage log book is and why you need one
A mileage log book is a record of the miles you drive for business, medical, or charitable purposes. The IRS does not require a specific format, but it does require that you keep one if you want to deduct mileage on your tax return. Without a log, you cannot prove to the IRS that the miles you claim actually happened.
The IRS is strict about mileage deductions because they are straightforward to overstate. A log book protects you in two ways: it gives you accurate numbers to report, and it gives you proof if the IRS ever asks questions about your return. Even a straightforward notebook counts, as long as it shows the date, destination, business purpose, and miles driven for each trip.
You do not need to log personal miles or commuting miles (the drive from home to your regular workplace). You only log miles that serve a business, medical, or charitable purpose. The IRS publishes a standard mileage rate each year—the amount you can deduct per mile—and you multiply that rate by your total logged miles to get your deduction.
Key Takeaways
- A mileage log must record the date, destination, business purpose, and miles for each trip; the IRS has no required format but requires proof if you claim mileage deductions.
- You log only business, medical, or charitable miles—not your regular commute or personal errands—and the IRS publishes a standard mileage rate each year that you multiply by your total miles.
- A straightforward notebook, spreadsheet, or app all work; what matters is that your entries are contemporaneous (written at or near the time of the trip) and consistent.
- If you are audited and cannot produce a log, the IRS will disallow your entire mileage deduction, so keeping records is the difference between a valid deduction and no deduction at all.
What information to record in each entry
Each trip needs four pieces of information: the date you drove, where you went, why you went there, and how many miles you drove. Write these down at the time of the trip or as soon as possible after—the IRS calls this a contemporaneous record, and it carries more weight than a log you reconstruct months later from memory.
The date is straightforward: write the calendar date. The destination should be specific enough that someone reading it understands where you went—"client office at 123 Main Street, Springfield" is better than "client meeting." The business purpose is the key field: write what you did there or why the trip was necessary. Examples include "client consultation," "medical appointment at Dr. Smith's office," "donation delivery to Goodwill," or "job interview at XYZ Company."
For miles, you can measure the actual distance using your odometer (record the starting and ending odometer reading), use a mapping tool like Google Maps, or rely on your car's trip computer if it tracks distance. The IRS does not require you to use one method over another, but your numbers should be reasonable and consistent. If you drive the same route regularly, you can log it once and note that it is a recurring trip, but the IRS prefers individual entries for each trip.
Choosing a format that works for you
You can keep a mileage log in a paper notebook, a spreadsheet, or a dedicated app. The format does not matter to the IRS as long as the information is there and you can produce it if asked.
A paper log is straightforward and requires no technology. Buy a small notebook you can keep in your car and write entries by hand. The downside is that it is straightforward to forget entries or lose the notebook, and you have to add up the miles yourself at tax time.
A spreadsheet (in Excel, Google Sheets, or similar) lets you organize entries by date and automatically sum your total miles. You can add columns for trip type (business, medical, charitable) and sort by category. The downside is that you have to remember to enter data regularly, and you need a device to record entries.
A mileage tracking app (such as MileIQ, Stride Health, or TripLog) can automatically log trips using your phone's GPS, or you can enter them manually. Many apps categorize trips, calculate totals, and generate reports you can read for your tax file. Some are free; others charge a monthly fee. The advantage is convenience and automatic calculation; the disadvantage is that you are relying on a third party to keep your data find and accessible.
How to organize and store your log
Keep your log in one place and update it regularly—weekly is better than waiting until tax time. If you use paper, store the notebook somewhere safe where you can find it when you need it. If you use a spreadsheet or app, save it in a location you can access again, and consider keeping a backup copy.
At the end of the tax year, add up your total miles by category (business, medical, charitable). The IRS allows different deduction rates for different purposes, so separating them now makes tax filing easier. If you use an app or spreadsheet, generate a summary or export showing your total miles and the dates covered.
Keep your log for at least three years after you file your tax return. The IRS can audit returns going back three years in most cases, and longer if they suspect underreporting of income. If you are audited and asked about mileage deductions, you will need to show your log to support the numbers you reported.
What the IRS standard mileage rate means for your deduction
Each year, the IRS publishes a standard mileage rate—a fixed dollar amount per mile that you can deduct for business, medical, or charitable driving. This rate changes annually and varies by purpose. For example, the rate for business miles is higher than the rate for medical miles, because business driving is considered a more direct business expense.
To calculate your deduction, multiply your total logged miles in each category by the rate for that category in the year you drove them. If you drove 5,000 business miles in 2024 and the business mileage rate for 2024 is $0.67 per mile (this is an example; check the IRS website for the actual current rate), your deduction would be $3,350. You report this on your tax return, usually on Schedule C if you are self-employed or on Schedule A if you are an employee claiming unreimbursed work expenses.
The standard mileage rate is an alternative to tracking actual expenses (gas, maintenance, insurance, depreciation). You cannot use both methods for the same vehicle in the same year. Most people find the standard mileage rate simpler because it requires only a mileage log, not receipts for every car expense.
Common mistakes to avoid when logging miles
The most common mistake is not logging at all, or logging only some trips and estimating the rest. The IRS will disallow an entire mileage deduction if your log is incomplete or unreliable. Log every trip that qualifies, even short ones.
Another mistake is logging commuting miles. The drive from your home to your regular workplace is not deductible, even if you work for yourself. However, if you drive from home to a temporary work location, or from one client to another, those miles count. The rule is: if the trip is between two work locations, it is deductible; if it is between home and a regular workplace, it is not.
A third mistake is vague business purposes. "Client meeting" is acceptable; "work" is not. The IRS wants to know what the trip was for, and a vague entry suggests you are not keeping a genuine record. Be specific about the client name, the type of appointment, or the reason for the trip.
Finally, do not reconstruct your log from memory months later. If you did not write down the miles at the time, do not add them now. A log that is clearly written after the fact is weaker evidence than one written contemporaneously, and the IRS may reject it entirely.
Mileage logs for different situations
If you are self-employed, you log all miles driven for your business and deduct them on Schedule C. This includes miles to client meetings, to a temporary work location, or to buy supplies for your business.
If you are an employee, you can deduct unreimbursed work-related miles only if your employer does not reimburse you and you itemize deductions on your tax return (rather than taking the standard deduction). This is less common now because the standard deduction is high for most filers, but it is still an option if your work-related miles are substantial.
If you drive for medical reasons—to appointments, to pick up prescriptions, to physical therapy—you can deduct those miles if you itemize. The medical mileage rate is lower than the business rate.
If you drive for charitable purposes—delivering donations, volunteering for a nonprofit, attending a charity event—you can deduct those miles if you itemize. The charitable mileage rate is fixed by law and does not change annually.
Frequently Asked Questions
Do I have to use a specific app or format for my mileage log?
No. The IRS does not require a specific format. A paper notebook, a spreadsheet, or an app all work equally well as long as you record the date, destination, business purpose, and miles for each trip. What matters is that your log is accurate, contemporaneous, and complete.
Can I estimate my mileage if I forget to write it down?
Not reliably. If you did not log a trip at the time, do not add it to your log later. The IRS prefers contemporaneous records and may reject estimates. If you forget to log a trip, accept the loss and log the next one on time.
What happens if I am audited and do not have a mileage log?
The IRS will disallow your entire mileage deduction. You cannot claim miles without proof, and a log is the only proof the IRS accepts. This is why keeping a log is essential if you plan to deduct mileage.
Can I deduct miles I drive from home to my regular job?
No. Commuting miles—the drive from home to your regular workplace—are never deductible. However, if you drive from home to a temporary work location, or from one client to another, those miles are deductible.
How long do I need to keep my mileage log?
Keep it for at least three years after you file your tax return. The IRS can audit returns going back three years in most cases, and you may need to show your log as proof of the deduction you claimed.