What the IRS actually wants in a mileage log

The tax code does not let you deduct car expenses on an estimate. Every business mile you claim has to be proved, and the rules say what the record of a drive has to show, when it has to be written, and how long to keep it. This piece goes through each rule and the source it comes from. The sources are listed at the end.

It is written for people who deduct a car on Schedule C: the self-employed, freelancers, gig drivers and single-member LLCs. An employee cannot deduct unreimbursed mileage on a federal return, apart from a few groups the law names, among them Armed Forces reservists, fee-basis state or local officials, certain performing artists and eligible educators. A law signed in July 2025 made that rule permanent.

What the IRS actually requires

The rule is in the tax code. Section 274(d) allows no deduction for “listed property” unless you substantiate it “by adequate records or by sufficient evidence corroborating the taxpayer’s own statement”. A car is listed property: section 280F(d)(4) puts “any passenger automobile” first on the list. What you have to substantiate is the amount, the time and place, and the business purpose.

The regulation that carries this out, 26 CFR 1.274-5T, explains why it is strict. Courts used to estimate a deduction when a taxpayer clearly had the expense but could not show how much, under a 1930 case, Cohan v. Commissioner. For cars the regulation “supersedes” that case: no deduction is allowed “on the basis of such approximations or unsupported testimony of the taxpayer.” Publication 463 puts it in one line: “You can’t deduct amounts that you approximate or estimate.”

It applies whichever method you use. You can deduct a car at the standard mileage rate, or at actual cost: the business share of fuel, repairs, insurance, depreciation and the rest. The standard rate spares you the fuel and repair receipts. It does not spare you the log. The regulation says a taxpayer on a mileage rate “will not be relieved of the requirement to substantiate the amount of each business use (i.e., the business mileage), or the time and business purpose of each use.” With actual costs you need the miles too, because the business share is worked out from them. Publication 463: “You can divide your expense based on the miles driven for each purpose.”

The rate depends on the date of the drive. For 2026 the business rate is 72.5¢ a mile through June 30, set by Notice 2026-10, and 76¢ a mile from July 1, set by Announcement 2026-11 after fuel prices rose. So a 2026 log is totaled in two halves. 10,000 business miles, half driven before July 1 and half after, come to 5,000 × 72.5¢ = $3,625 plus 5,000 × 76¢ = $3,800, which is $7,425. Business parking and tolls are added on top, at what you paid.

The standard rate has conditions of its own. You cannot use it if you use five or more cars at the same time, or for a car you have depreciated under MACRS or claimed a section 179 deduction or the special depreciation allowance on. For a car you own, you have to choose it in the first year the car is available for use in your business. If you use it for a leased car, you have to use it for the whole lease. Chapter 4 of Publication 463 has the full list.

The four things every trip needs

Publication 463 turns the statute into a table, Table 5-1, How To Prove Certain Business Expenses. For a car, each business drive needs:

Element	What Table 5-1 asks for
The date	“the date of the use of the car”
The miles	“the mileage for each business use”
Where you went	“Your business destination”
Why	“Business purpose for the expense”

The purpose is the one element a phone cannot know on its own. What to write there has a piece of its own.

The regulation behind the table, 1.274-5T(b)(6), also asks for “the total use of the listed property for the taxable period”: a figure for the car, not for a drive.

Once a year, for each car

• Total miles for the year. Table 5-1 asks for “the total miles for the year” as well as the business miles.
• The date the car went into business use. Table 5-1 lists “the date you started using it for business”.

The return asks for both. Part IV of Schedule C has these lines, the same on the 2025 form and on the 2026 draft:

• 43: “When did you place your vehicle in service for business purposes?”
• 44: the miles you drove the vehicle during the year, split into a business, b commuting and c other.
• 45: “Was your vehicle available for personal use during off-duty hours?”
• 46: “Do you (or your spouse) have another vehicle available for personal use?”
• 47a: “Do you have evidence to support your deduction?”
• 47b: “If ‘Yes,’ is the evidence written?”

Part IV is for a return that takes the standard rate, or has a leased or fully depreciated car. If you depreciate the car, or file Form 4562 for another reason, Form 4562, Part V asks much the same questions instead. With more than one car, you attach the same information for each additional one.

Nothing in the rules requires odometer readings. Even so, the simplest proof of a year’s total is the odometer on January 1 and on December 31. The sample log in Publication 463 (Table 5-2, an example worksheet, not an official form) has a column for the odometer at the start and at the stop of each trip.

Parking and tolls

Publication 463: “In addition to using the standard mileage rate, you can deduct any business-related parking fees and tolls.” Parking at your regular place of work is commuting, and does not count.

Each fee is an expense of its own, so log it with the drive it belongs to. You need a receipt, bill or similar evidence for one of $75 or more, unless no receipt is readily available. Below $75, the entry in your log is the record.

Round trips and regular routes

• A round trip is one use. The regulation lets “a round trip or uninterrupted business use” be “accounted for by a single record”. It also says a stop for lunch on the way between two business stops “is not an interruption of business use.”
• An established route needs less. For a regular sales or delivery route, Publication 463 lets you record “the length of the delivery route once, the date of each trip at or near the time of the trips, and the total miles you drove the car during the tax year.”

What counts as a business mile?

A log only helps with miles that are deductible in the first place.

Commuting is not. Driving between home and your main or regular place of work is personal, and Publication 463 says “You can’t deduct commuting expenses no matter how far your home is from your regular place of work.” Working on the way does not change that: the same applies “even if you work during the commuting trip”, and the example it gives is making business calls on your phone.

Business drives include driving from one workplace to another, to clients or customers, and to a business meeting away from your regular workplace. For a drive that starts or ends at home, the Schedule C instructions for line 44b list three cases that are not commuting:

1. You have at least one regular work location away from home, and you drive to a temporary work location in the same trade or business, however far it is.
2. You drive to a temporary work location outside the metropolitan area where you live and normally work.
3. Your home is your principal place of business, under the same test as the home office deduction, and you drive to another work location in the same trade or business, regular or temporary, however far it is.

A temporary work location is generally one where the work is expected to last a year or less.

No regular office? If you have no regular office and no office at home, Publication 463 treats your first business stop of the day inside the metropolitan area as your office. The drive from home to that stop, and from the last stop back home, are commuting. The drives between stops are business.

When it has to be written down

The regulation uses the word “contemporaneous” once, and it says “A contemporaneous log is not required.” What it asks for is a log kept “in such manner that each recording of an element of an expenditure or use is made at or near the time of the expenditure or use.” It defines “at or near the time” by memory rather than by the clock. It means a time when you have “full present knowledge” of each element, and it gives an example: “a log maintained on a weekly basis, which accounts for use during the week, shall be considered a record made at or near the time of such use.” Publication 463 says the same in plain English: “You don’t need to write down the elements of every expense on the day of the expense.”

So filling in the log once a week is enough. What the timing buys is weight. The sentence that says a contemporaneous log is not required goes on to say that a record made at or near the time, supported by sufficient documentary evidence, “has a high degree of credibility not present with respect to a statement prepared subsequent thereto when generally there is a lack of accurate recall.” A log written up the following April is that later statement.

A missed week does not spoil the rest. The rules look at each element of each drive. The weeks you logged are still an adequate record. The drives from the week you missed have to be proved some other way, which is the next section.

Paper, a spreadsheet and an app all count. The first things the regulation names as an adequate record are “an account book, diary, log, statement of expense, trip sheets, or similar record”. An adequate record generally has to be written, but “a record of the business use of listed property, such as a computer or automobile, prepared in a computer memory device with the aid of a logging program will constitute an adequate record.” An electronic record has the same duties as a paper one. Publication 583 says the system has to “index, store, preserve, retrieve, and reproduce” the records “in legible format.” The rules say nothing about GPS. For a log kept by hand there is a printable mileage log with the columns these rules ask for, and the same columns as a CSV; what each column is for has a piece of its own.

Confidential details can live elsewhere. If an element is confidential, such as a patient’s name, it does not have to be in the log itself. Publication 463 says you “do have to record the information elsewhere at or near the time”.

Two ways to prove a drive

Section 274(d) gives two routes, and the regulation spells out both.

Adequate records. This is a log, plus documentary evidence where it is needed, which “in combination, are sufficient to establish each element”. For standard-rate miles, the log is nearly all of it. The documents are the receipts for parking and tolls of $75 or more. This is the route a mileage log is for.

Your own statement, backed by other evidence. Without an adequate record, each element can still be proved by your own statement, “whether written or oral, containing specific information in detail”, together with other evidence that corroborates it. For the date, the place and the miles, that evidence has to be direct: documents, or someone else’s detailed written statement or testimony. For the business purpose it can be circumstantial. Publication 463 gives an example: for someone making deliveries, the nature of the work shows the car was used for business, and “Invoices of deliveries establish when you used the car for business.”

Sampling. You can keep an adequate record for part of the year and use it to prove the whole year, if other evidence shows that the part is representative. In the Publication 463 example, a record kept for the first week of each month shows 75% business use, and invoices and bills show the same pattern for the rest of each month. In a counter-example in the regulation, a salesman keeps records only for the fourth week of each month, when he delivers the orders taken the month before, and they show 70% business use. That does not prove the year, “because use during this week is not representative of use during other periods.” A sample is easier to defend for a steady routine than for a varied one.

A log rebuilt after the fact

A log reconstructed months later is not an adequate record, and it cannot be an estimate. What it can be is the second route above. It is your own detailed statement, rebuilt drive by drive from things you kept at the time, such as calendar entries, invoices, client emails, receipts, or a delivery app’s trip history. It counts only as far as that evidence backs up each element. The regulation sets a high bar: evidence for a statement not made at or near the time “must have a high degree of probative value to elevate such statement and evidence to the level of credibility reflected by a record made at or near the time”.

Rebuilding is a right in one case only. If your records were lost “through circumstances beyond the taxpayer’s control, such as destruction by fire, flood, earthquake, or other casualty”, you “shall have a right to substantiate a deduction by reasonable reconstruction”. A notebook that was never filled in is not that case.

What happens to a drive you can’t prove

The deduction for it is not allowed, and no part of it can be allowed on an estimate instead. That is what the rule against approximations means. At the 2026 rates, each business mile you cannot prove is 72.5¢ of deduction lost if it was driven before July 1, and 76¢ after.

A penalty can come on top. Section 6662 adds 20% of the part of an underpayment caused by “negligence or disregard of rules or regulations”. The regulation under it counts as negligence “any failure by the taxpayer to keep adequate books and records or to substantiate items properly.” The penalty is not automatic, but a missing log is one of the things it covers.

The return asks about the log directly: lines 47a and 47b of Schedule C ask whether you have evidence, and whether it is written. You sign the return with those answers on it.

Keep records for years, not months

Publication 463 says to keep records “for 3 years from the date you file the income tax return on which the deduction is claimed. A return filed early is considered filed on the due date.” That is the general period in which the IRS can assess more tax, under section 6501. The IRS page How long should I keep records? lists the cases that run longer, and its page on audits adds the last one:

Situation	Keep the log for
Most returns	3 years from the date you file, or from the due date if you file early
You file a claim for a refund after filing	3 years from filing, or 2 years from paying the tax, whichever is later
You leave out income of more than 25% of the gross income shown on the return	6 years
A fraudulent return, or no return	No limit
An audit that is not resolved, when you agree to extend the period	Until the extended period ends

For a 2026 log the clock starts at the 2027 filing, not at the drives. A return filed by April 15, 2027 is open until April 15, 2030. One filed on extension in October 2027 is open until October 2030.

Two cases are specific to the car:

• Depreciation. If you deduct actual costs and depreciate the car, Publication 463 says to keep records of its business use “for each year of the recovery period”. Publication 946 says that for listed property you keep them “for as long as any recapture can still occur.”
• The car’s basis. Standard-rate miles lower the car’s basis too, because part of the rate counts as depreciation. Notice 2026-10 puts it at 35¢ a mile for 2026 and 33¢ for 2025. That matters when you sell the car, or switch it to actual costs. The IRS says to keep records relating to property “until the period of limitations expires for the year in which you dispose of the property”, so keep every year’s business-mile total until then.

In OdoTax

OdoTax records most of the log as you drive. The rest is yours to add. What the finished log looks like is on a page of its own.

• It detects drives as they happen and records, for each one, the date, where it started and ended, the route and the miles. A drive you add by hand is marked with an asterisk in the report, which says how many were entered that way.
• The purpose is a line you add to each business drive. A frequent drive, which is a route saved with its category and purpose, files every drive on that route with its purpose. A business drive with no purpose shows Not recorded in the report, which also counts how many there are.
• Drives between home and your regular workplace go under Commute, so the report can split the year into business, commuting and other miles. Once you name the two places as Home and Work, OdoTax suggests Commute for those drives.
• Parking and tolls you enter on a business drive are added at what you paid. OdoTax records the amounts, not the paper, so keep the receipts yourself.
• Each drive is priced at the IRS rate in force on its date, so a 2026 report works each half of the year at its own rate.
• The report’s vehicle table has what Part IV asks for on lines 43–44c: when each car went into business use, its odometer at the start and end of the period, and its business, commute and other miles. You add odometer readings under Settings → Odometer, and the in-service date on the vehicle in the web account (In business use since). Business and commute are the drives OdoTax recorded. With a reading at the start and the end of the period, a report of all drives takes the other miles from the odometer, its miles less business and commuting, so the three add up to the car’s total even when it was driven without the phone.
• The last page prints the questions from lines 45–47b, with boxes to tick.
• The report exports as PDF and CSV. Keep a copy with the return you file, for as long as the table above says.

The bottom line

For each business drive, the log needs the date, the miles, the destination and the purpose, written down while you still remember them. A weekly log counts. For each car and year, it needs the total miles, split into business, commuting and other, and the date the car went into business use. Add parking and tolls, with receipts from $75. Keep it all for at least three years from the day you file. A drive you cannot prove is not deductible, and an estimate cannot take its place.

Sources

• IRS, Publication 463: Travel, Gift, and Car Expenses (2025): chapter 4, Transportation and Car Expenses (commuting, temporary work locations, the standard mileage rate, parking fees and tolls, dividing expenses by miles); chapter 5, Recordkeeping (Table 5-1, Timely kept records, Confidential information, What if I Have Incomplete Records?, Sampling, Destroyed records, Car expenses, How Long To Keep Records and Receipts, Table 5-2).
• IRS, Notice 2026-10 (the 2026 standard mileage rates, the depreciation part of the rate, and unreimbursed employee expenses) and Announcement 2026-11, I.R.B. 2026-29 (the rates from July 1, 2026).
• IRS, Instructions for Schedule C (Form 1040): line 9, and Part IV, lines 44b and 47; Schedule C (Form 1040), Part IV, lines 43–47b, and the 2026 draft.
• IRS, Instructions for Form 4562: Part V, Listed Property.
• IRS, Publication 583: Starting a Business and Keeping Records: Electronic records.
• IRS, Publication 946: How To Depreciate Property: chapter 5, What Records Must Be Kept?
• IRS, Topic no. 510, Business use of car and Topic no. 305, Recordkeeping.
• IRS, How long should I keep records? and IRS audits.
• 26 U.S. Code § 274(d): substantiation required for listed property; § 280F(d)(4): a car is listed property.
• 26 CFR § 1.274-5T: (a) no deduction on approximations; (b)(6) the elements for a car; (c)(1) “A contemporaneous log is not required”; (c)(2) adequate records, the weekly log, computer records, the established route; (c)(3) your own statement with corroborating evidence, and sampling; (c)(5) records lost to a casualty; (c)(6) one record for a round trip. 26 CFR § 1.274-5: (c)(2)(iii) documentary evidence at $75; (j)(2) the mileage rate does not replace the log.
• 26 U.S. Code § 6501: the 3-year, 6-year and unlimited periods for assessing tax.
• 26 U.S. Code § 6662 and 26 CFR § 1.6662-3: the 20% accuracy-related penalty; negligence includes failing to keep adequate records.

This article is general information, not tax advice. Tax situations vary — check with a qualified professional before you file.