What a mileage log is and why you need one
A mileage log is a record of the miles you drive for business, medical, charitable, or moving purposes. The IRS requires you to keep one if you want to deduct those miles on your tax return. Without a log, the IRS will not accept your mileage deduction — they want proof that the miles actually happened, not just your word.
The log does not have to be fancy. It can be a notebook, a spreadsheet, a note in your phone, or a dedicated app. What matters is that you record four pieces of information for each trip: the date, the starting and ending odometer readings (or total miles driven), the destination, and the business purpose. The IRS calls this the "contemporaneous" record — meaning you write it down at the time or very soon after, not months later when you are preparing your taxes.
Different types of driving have different deduction rates. Business mileage, medical mileage, and charitable mileage each have their own rate set by the IRS each year. Moving mileage (for a job-related move) is also deductible in some cases. Your log needs to separate these categories so you can add them up correctly when you file.
Key Takeaways
- You must record the date, odometer readings, destination, and business purpose for each trip — writing it down at the time or shortly after is required by the IRS.
- Different types of driving (business, medical, charitable, moving) have different deduction rates and must be tracked separately in your log.
- A mileage log can be a notebook, spreadsheet, or app — the format does not matter as long as you have the four required details for each trip.
- The IRS will reject a mileage deduction if you cannot show a contemporaneous record, so starting your log before you need it is far easier than reconstructing one later.
What information to record for each trip
Every entry in your mileage log needs four pieces of information. First, the date — the day you took the trip. Second, the odometer readings — the number on your car's odometer when you started and when you ended, or straightforward the total miles for that trip. Third, the destination — where you went. Fourth, the business purpose — why you went there.
The business purpose is where people often get vague. "Meeting" or "work" is not specific enough. Write down what the meeting was about, who you met with, or what task you were doing. Examples: "Client meeting with ABC Corp about contract renewal," "Drove to medical clinic for annual checkup," "Drove supplies to food bank donation center," "Drove to new job location for relocation." The IRS wants enough detail that someone reading your log could understand why the trip was necessary.
You do not need to record the time of day, the route you took, or the cost of gas. Those details are not required. Stick to the four essentials and you will have what the IRS needs to see.
How to set up your log format
The simplest format is a table with five columns: Date, Starting Odometer, Ending Odometer, Destination, and Business Purpose. If you prefer, you can use Total Miles instead of separate starting and ending readings — just make sure you are recording actual miles, not estimates. Add a sixth column for the trip category (Business, Medical, Charitable, Moving) so you can sort and total them later.
If you use a notebook, draw the columns by hand or print a template. If you use a spreadsheet (Google Sheets, Excel, or similar), set up the columns once and copy the row down as you add trips. Many people find a spreadsheet easier because you can use formulas to add up miles by category automatically.
Phone apps designed for mileage tracking (such as MileIQ, Stride Health, or TripLog) will do the recording for you — some can detect when you start driving and prompt you to categorize the trip. These apps store your log in the cloud, which means you cannot lose it if your phone breaks. However, you will still need to review each trip and confirm the purpose, because the app cannot know why you drove somewhere.
Whichever format you choose, keep it accessible. If your log is buried in a file you never look at, you will forget to record trips. Keep it somewhere you see it regularly — on your desk, in your car, or on your phone's home screen.
When and how often to record your trips
Record each trip on the day you take it, or within a day or two at most. The IRS expects a "contemporaneous" record, which means written down at or near the time it happened. If you wait weeks or months to fill in your log, the IRS may not accept it, because they cannot tell whether you are remembering accurately or guessing.
If you drive multiple trips in one day, record each one separately. If you drive to the office and then to a client meeting and then home, that is three separate trips with three separate entries. Do not lump them together as "drove for work today."
At the end of each month, add up the miles in each category (business, medical, charitable, moving). This gives you a monthly total to check against and makes it easier to spot if you missed recording a trip. If you drove to the same place multiple times in a month, you should still have a separate entry for each trip — do not combine them into one line.
What to do if you missed recording some trips
If you realize you forgot to log a trip, you can reconstruct it if you have other evidence. A calendar entry, an email confirming a meeting, a receipt from a store you visited, or a text message about where you were going can all help you remember the date and destination. Write the trip into your log and note that you reconstructed it from other records.
The IRS understands that people forget to write things down. What they will not accept is a log that is clearly made up months later with no supporting evidence. If you have a pattern of missing trips or if your reconstructed entries do not match any other records, the IRS may reject the whole deduction.
The best approach is to start logging when ready, even if you are only a few weeks into the year. A log that covers most of your trips is far better than one that covers none of them. If you missed the first two months of the year, start logging now and deduct only the miles you have recorded.
Keeping your log safe and organized for tax time
Your mileage log is a tax document. Keep it in the same place where you store other tax records — receipts, invoices, bank statements, and so on. If you use a paper notebook, store it in a folder or file box. If you use a spreadsheet or app, back it up (print a copy or save it to cloud storage) so you do not lose it if your computer or phone fails.
At the end of the year, total up the miles in each category. Create a summary that shows: total business miles, total medical miles, total charitable miles, and total moving miles (if any). This summary is what you will reference when you fill out your tax return. You do not send the entire log to the IRS unless they ask for it, but you need to have it available if they request proof of your deduction.
Keep your mileage log for at least three years after you file your tax return. The IRS can audit your return for up to three years after you submit it, and they may ask to see your log. If you cannot produce it, they will disallow the deduction and you may owe back taxes plus penalties.
Common mistakes to avoid
Do not estimate your mileage. Use your actual odometer readings. If you cannot see your odometer clearly or your car does not have one, write down the miles as accurately as you can and note that you estimated. The IRS prefers actual readings, but a reasonable estimate with a note is better than nothing.
Do not mix personal and business miles in a single entry. If you drove to the grocery store and then to a client meeting, those are two separate trips. Only the client meeting trip counts as business mileage.
Do not wait until tax time to start your log. If you have not been recording miles all year and suddenly create a log in March, the IRS will be skeptical. Start logging now, even if it is mid-year.
Do not forget to separate your trip categories. If you log all your driving as "business" when some of it was personal, your deduction will be wrong. Take the extra 10 seconds to write down the correct category for each trip.
Frequently Asked Questions
Can I use my car's built-in trip computer or GPS instead of writing down odometer readings?
A trip computer or GPS can help you confirm the miles you drove, but the IRS still wants you to record the date, destination, and business purpose in writing. Use the technology to double-check your math, but keep a written log with all four required details for each trip.
What if I drive the same route to the same client every week — do I have to log every single trip?
Yes. Each trip is a separate entry in your log, even if you drive the same route to the same place every week. The IRS wants to see that you actually made the trips, not just that you could have made them. One entry per trip is the rule.
Can I deduct miles I drove last year if I did not keep a log at the time?
It is very difficult. The IRS requires a contemporaneous record, which means written down at or near the time. If you did not log your miles in the year you drove them, you can try to reconstruct the log using calendars, emails, receipts, or other evidence, but the IRS may reject it. It is much easier to start logging now for this year and future years.
Do I need to keep receipts for gas or maintenance along with my mileage log?
No. The mileage deduction is separate from gas and maintenance receipts. You deduct either the standard mileage rate (a fixed amount per mile set by the IRS) or your actual expenses (gas, maintenance, insurance, depreciation), but not both. If you use the standard rate, you only need your mileage log. If you use actual expenses, you need receipts, but you do not need a mileage log.
What if my employer reimburses me for mileage — do I still need to log it?
If your employer reimburses you at or below the IRS standard mileage rate and you do not deduct the miles on your tax return, you do not need a log for tax purposes. However, you may still want to keep one for your own records to make sure the reimbursement is correct. Check with your employer or tax preparer about what they require.